A light vegetarian sandwich with great flavor that is perfect for summer. You can use just about any type of bread but Kaiser rolls or burger buns are best. I like to serve this with grilled squash and a glass of white wine!

Grilled Portobello with Basil Mayonnaise Sandwich

balsamic vinegar

olive oil

garlic

portobello mushroom caps

mayonnaise

Dijon mustard

lemon juice

basil

kaiser rolls, split, toasted

butter

lettuce

tomato

Preheat an outdoor grill for medium heat, and lightly oil the grate. Whisk together the balsamic vinegar, olive oil, and garlic in a small bowl.


Arrange the portobello mushrooms gill-side up on a tray or baking sheet. Brush the mushrooms with some of the vinegar mixture, and allow to marinate for 3 to 5 minutes.


Place the marinated mushrooms on the preheated grill, gill-side down. Grill mushrooms until tender, brushing both sides of the mushrooms with the remaining marinade, about 4 minutes on each side.


Mix the mayonnaise, dijon mustard, lemon juice, and basil in a small bowl. Butter the toasted kaiser rolls, then spread with the mayonnaise mixture. Divide the mushrooms, lettuce, and tomato slices evenly to make 6 sandwiches.


I've made this recipe several times already this summer, and it is delicious! The only change I made was not buttering the buns, and toasting them on the grill. The mayo combo is so good, I use it on other veggie sandwiches. Thanks for the great recipe.

DEEEEELICIOUS! The basil mayo makes this sandwich, and just puts it over the top. I used sliced portobello mushrooms because that's all the store had this week. I marinated them in the basalmic mixture for about an hour before cooking and they had a wonderful flavor. I did decrease the olive oil to about 2 tbsps. because I was trying to watch the fat and I used light mayo in the basil mayo with great results. This is a definate keeper! Thanks for sharing. :)

Delicious! Very satisfying on a hot summer night. The only changes I made were 1) to marinade the mushrooms in the vinegar/oil/garlic for 2 hours instead of just brushing it on before grilling. The mushrooms were very flavorful that way, and 2) to add a slight amount of cheese (pick your favorite) onto the mushrooms just before taking off the grill. I loved the mayo, and will look for other ways to use it!

Scrumptious!  I enjoyed mine exactly as the recipe was written; my husband and kids wanted to put some cheese on their mushrooms as they were grilling (Swiss).  High fives all around ... we will absolutely make again.  Thank you for the recipe!

Edit here ... I should have added that I did marinate the mushrooms for a couple of hours before grilling.   I think that helped a lot, an will deflinitely do it again next time, too, for sure.   Enjoy, enjoy everyone ... this recipe is a winner.  :-)

I thought this was a great "burger"!  I have always loved portobello sandwiches and this was no different.  It was very easy to make, especially the smaller portobellos.  I'm not sure how to tell when the mushroom, especially the big ones, are fully cooked, so I think some of the big, thick ones didn't turn out as well as the smaller ones.  I would make these again, but I think next time I'll also marinate some red onions in the same sauce and throw them on the "burger".

The best portobello sandwich I ever had! I served it on artisan bread, warm from the grill. I made bruschetta with the leftover bread and basil, but used that as the bun for my leftover portobellos. So it became a bruschetta portobello burger- heaven! This is a new summer grilling staple at our place. My three year old loved it, but he's an adventurous eater- as for my husband, he's a corn dog man, so this didn't exactly fly for him. But those with a love for gourmet will find this to be kickin!

WOW - these are fabulous! I love portobello mushrooms, so I had to give this a try. Plus they're so easy to put together. It's great for lunch or a quick weeknight meal. I would recommend marinating the mushrooms for a couple of hours vs. a few minutes. Don't skip the basil mayo, it's awesome! I used Hellman's light mayo and toasted some sesame seed rolls then added a slice of provolone along with the rest of the ingredients. These are so good, you'll never miss the meat!

Great recipe! First time we made it we accidentally mixed all ingredients together and cooked the mushrooms in all of it instead of having the mayo mix on its own. They were actually better this way!

Wow. I almost didn't make the mayo as I don't typically put mayo on my burgers, but I think this added to perfection!  I made a lot more marinade mix than the recipe called for to help coat the top.

This was easy, and delicious.  I've made it twice, exactly as written - no changes.  I toyed with the idea of adding a slice of melty cheese, but haven't yet.  I like the idea of a mostly vegan meal as I am exploring more meat-free dishes.  Really though, you almost think you are eating a savory piece of meat in this sandwich!  Thanks!

FANTASTIC!!! The balsamic/olive oil marinade on the portobellos is something I've done before and loved; but as absolutely simple as the basil mayo is, that is what takes this over the top. I added a slice of pepperjack and skipped buttering the buns. Will make again and again. Thanks :)

I didn't think it was possible, but this REALLY does have a steak flavor.  Delicious.  I am craving it again!  Even my son who doesn't like mushrooms enjoyed trying this.  Too bad they were all gone before he mustered his food courage and tried the last little nibble.

Great recipe! Quick, easy and oh so tasty!

I sized this down for two so it may have adjusted the taste. But i thought this was wonderful. The mushroom was juicy and the may was a perfect complement. I will make again.

Delicious! I jut made this for my husband who thinks there should be meat in every meal. This changed his mind and will now be on our weekly menu! Meat will not be missed!

I've made portobello sandwiches for years and have to admit the basil mayo really puts a twist in them.  Am definitely keeping this as my new favorite way to serve them.  I didn't have any buns so used crusty Italian bread that I brushed with olive oil and toasted on the grill for a few minutes.  Outstanding!

Absolutley loved this one! I bought 2 huge portobello mushrooms to grill. The basil mayo rocks out....I used low fat mayo and fresh lemon juice and fresh basil....which I always think is key to get the best flavors....I served on a whole wheat sandwich thin (Arnold brand). Nice summer dinner! Thanks!

the sauce...mayo/basil/lemon was nice, everyone liked the sauce however the balsalmic vinegar did not go over. I've had much better portabello's and this wasn't one. I'd ditch the vinegar.

SO good and SO easy!!  I made this Saturday, and I liked it so much I am making it again tonight!  I took the advice of some other reviewers and marinated mine for about three hours.  The basil mayo is what really makes this five stars.  Thanks for sharing!!

Fantastic! I don't have a grill so I sauteed the mushrooms. It's a bit more messy but gets the job done. I also put this on homemade bread that I made in my bread machine and it was even better than the first time I made this recipe. Delish!

Excellent and fast!   I put basil leaves on the sandwich rather than chopping for the mayo.   Also added garlic salt  and fresh mozzarella.

I did not change any of the ingredients and it was delicious.  I will definitely make again.   I had never grilled a portabella before so checked on line and most articles said to peal the top skin off.  It came off so easy.  Since it was so large, I grilled each side 7 minutes and it was perfect.  I put the marinade on a half hour before grilling.

My husband and I just discovered the beauty that is the portobello when he ordered it at a restaurant a few months ago.  I made this tonight (scaled down for two people), and we both loved it- especially the basil mayo- that really made the sandwich!  The only thing I'll do different next time is to use less balsamic vinegar when marinating the mushrooms.  While we both love balsamic, we thought the flavor was a bit too overpowering.  Great recipe though, thanks!  I'm sure I'll make it again soon!

My husband and I love this recipe!!! We have made it several times and LOVE them everytime! Will continue to make these for years to come!

Delicious! I did sub red wine vinegar for the balsamic. I had one mushroom after a short marinade. Then I had two that were marinated for a few days. I preferred the longer marinated ones. I didn't serve on a roll this time but atop some field greens with EVOO, balsamic, sea salt, black pepper and assorted olives. Will definitely try on the roll another time. The basil mayo goes great with the mushrooms. Thank you for the recipe, Rotorwife!

Loveeee it!!!  Thanks for great recipe! Will definitely make again and again :)

This was really tasty, we really enjoyed it.

I would give this 10 stars if I could! Fabulous! I've never touched a portobello mushroom (I don't even like mushrooms) but I am SO glad I tried this recipe. I let them marinate for a few hours as other reviewers suggested.

Loved it!!! I was so proud of myself! loved the dressing!! Thanks!

Next time I'll add more basil to the mayo mixture since I thought the basil flavor was really light.  Easy to make and quick to prepare!

I love the basil mayo and the portobello tasted better than a regular burger!

This sandwich was very easy to make and has a perfect balance of flavors.  It is delicious.  Probably the best Portobello sandwich I have had.

The mayo made this sandwich, without it it would have been fairly bland.

Delicious!  Added roasted onions and red peppper along with some pepper jack cheese.  Just toasted the buns instead of butter and used FF Mayo.  Great meatless dinner!  My rolls were larger than hamburger buns, so next time I will cook more portabellas.

Very good sandwich and unique!  I let the mushrooms marinate for a few hours and they were very juicy and delicious!!  Thanks for a great recipe!

I am a meat lover, recently we have been trying to cut back and I figure I would give this a try....honestly I was apprehensive. We LOVED it!! It tastes like beef, actually better!!

This was delicious! It had a lot of flavor and it was more filling than I thought it would be.

excellent, and very easy!  We halved the marinade and used 2 large portobello caps.  We used dried basil instead of fresh or the mayo as that's what we had (fresh would be yummy too).  I have a feeling we will be making this often.

Scrumptious. Added salt and pepper to the mushroom caps and to the mayo / dijon mixture.  I also used only about 1/4 cup of mayo but kept the other sauce proportions the same.  I prefer that the basil and dijon be stronger and less diluted.  Ate with provolone cheese.  Super tasty and a good deviation from the norm. I'll definitely make this again!

This was just okay. Not bad but not super great.

Unbelievably amazing!!! Love it! Also obsessed with the basil mayo- use it for everything! I like to grill chicken cutlets with a little salt and pepper and pair it with the mayo. This recipe is super easy to make and deliciously tasty. Highly recommend!

Followed recipe exactly and everyone flipped for it - including our usual "just meat &amp; potatoes" men.  Next time, will double the sauce.

This sounded SO good.  I think I should have read the other reviews first.  I think the Portobello's should defiantly marinate.  I did not marinate them and there wasn't enough flavor.  But the Basil Mayo is FANTASTIC!  I put a little black pepper in it and it was that much better. I am going to find different ways to use it (YUMMY).  

I am going to try this recipe again but next time I am going to try slicing the Portobellos and marinating them a lot longer so they soak up the marinade.  Plus I think adding a little salt to the marinade would really bring out the flavors.

Delicious! I didn't use butter because the oil and mayo were more than enough. I also did as others said and marinated the mushrooms for a few hours, along with peppers and onions. It turned out great.

This was delicious..did not miss the meat at all.  I made the recipe exactly as written but will add some swiss or provolone cheese next time

Wow, so good!  I added a bit of minced garlic to the mayo mixture, skipped grilling the buns and subbed roasted red peppers and mozzarella for the lettuce and tomato.  Couldn't believe what a quick and delicious meal this was - thanks!

The sauce definetly makes this burger.  I am allergic to mustard so I used worcheshire sauce and I didn't have any lemon juice so I just threw in some fresh lemon basil.  Tasted great!

This was amazing! I have made marinated portobellos before, and the vinegar was overwhelming - this was just right!  I marinated the portobellos for an hour, then pan-fried them with 1 Tbl. olive oil (covered) for about 6 minutes on each side, then sprinkled with a little bit of salt.  I left off the butter on the rolls because I didn't think it was necessary (and is just added fat).  The basil-mayonnaise was the perfect touch.  Thanks for the recipe!

Sauce was very good. I used a little less vinegar in the marinade and added some sea salt and ground pepper. Topped mushroom with mozzarella and red onion and tomato. It is amazing how much this sandwich fills you up. Could eat these all summer long.

I cooked these inside on the skillet since DH wasn't home from work yet and he is the grill master.  They turned out great.  I did marinate for about 15 minutes.

These were soooo good! I cooked the mushrooms in a pan for lack of a grill. I also threw in some baby bell peppers which were a perfect accompaniment.

This was THE BEST! I loved every bite, and was actually sad when I was done eating! I will be making this again, and again! Thank you for an awesome recipe :)

This was delicious! We used small buns so there was less bread. Super good!!!!

Mushrooms w/marinade was really good. Too much mayo for my taste in the basil mayonnaise. Next time I'll cut the mayo in 1/2.

Excellent- tastes a lot like grilled steak. The marinade is very versatile for grilled meats too.

NEW FAVORITE! This was simple and delicious. Will be in our regular meal rotation from now on.

Oh MY GOODNESSSSSSS  GRACIOUS! This is amazing. Seriously one of my favorite things I've eaten in quite a while. So good it's ridiculous.
We used honey wheat rolls instead of kaizer.  Butter was very unnecessary considering there was the mayo spread. The flavors in this come together beautifully

My family loved this recipe. The dressing is so good and really makes the sandwich tasty. I wanted to make it again tonight!

This was unbelievable. I was concerned that the texture would be weird but it was perfect. I added tarragon to the mix because that’s one of my favorite herbs. I also used some of the mayonnaise mixture (instead of butter) on the buns before browning in a pan. I find using mayonnaise helps so much with the flavor. I used baby spinach, red onions, tomato and slivers of Asiago cheese. I will be making this many more times.

Excellent burger!  Will be making many more times!

Very tasty! It was a big hit with my family!

Easy and tasty. I cooked the mushrooms longer than it said to. Maybe mine were thicker or my fire not so hot. But turned out very tasty. I didn’t butter my rolls.

We tried this for one of our meatless meals and it was delish! We love mushrooms but the basil sauce was the finishing touch.  Will definitely be making again@

This recipe is awesome.  The mayo-based sauce is savory and tangy.  I followed the recipe exactly and even toasted the buns on the grill.  I will definitely make this again!

This recipe was awesome. We broiled ours in the toaster oven. The sauce is really good and is now used for other sandwiches.

8-15-11:  Ann said this was excellent, even though I undercooked them and had to put them back on the grill.

I used a egg free mayo.  My husband and my neighbors all loved these.

This is so simple, elegant.  Yes mam you hit it out of the park.

This was very good and easy. I also grilled some zucchini and squash and served with it. I will definitely make it again!

Very good recipe. I followed the recipe exactly. ...and to think, I'm all about beef!

Just added red onion. Great alternative  to a hamburger

Fantastic!  I've tried several veggie grilled sandwiches that I've made myself or tried at restaurants.  This recipe is by far the best.  Lots of flavor.  The basil mayo sauce is so tasty that it will become my go to sauce for sandwiches and as a dip.

I used portobello mushrooms as big as a kaiser bun. I took the stems off and then marinaded them all day, gill side up, to soak in the marinade. 
I didn't use garlic and I didn't butter the buns.
I followed the rest of the recipe. They were delicious. The basil mayo really compliments the marinaded mushroom flavor.

Made this exactly as written.  My BF had never had grilled portobello mushrooms so was a bit skeptical and loved them.  When I asked him if he would eat it again, "Most definitely" were his words.  I would, however, add a touch of salt after putting the tomato slices on.

If you peel the outer layer of skin off of the larger portobello it is easier to eat.

This is a great recipe. Make sure you like the balsamic vinegar you use.  I used another when I didn't have and couldn't fine my preferred Regina brand.
 I've used the mayo sauce  on other sandwiches too.

Amazing!  Could rival any burger I have ever eaten!  Did sub the dijon/mayo combo for a garlic mayo with parsley.  So good...

Will definitely make again!  Excellent flavors!  Didn't measure anything for mayo.  Went a little heavy on basil-but I'll do it the same way next time.

This was great! Made no changes just additions, we added fresh mozzarella slices, warmed roasted peppers and grilled asparagus and red onion. Even my skeptical husband enjoyed it!

Loved this recipe! Easy and yummy. Served them on sour dough bread (that's what I had) still yum. If I had to change anything, I would maybe add a little more fresh basil to the "dressing" but that's just a preference.

This burger is out of this world! I've made it as written as well as with veganaise in place of mayo and it was great both ways! The marinade for the portobello mushroom is buttery and tangy! The Basil Mayo spread is so good we put it on our burgers, grilled corn and even baked potatoes. It's so light and the fresh basil adds a little something special. Better than any restaurant  Portobello burger I've had. Thank you! This one's a keeper!

Loved the flavor!! I had trouble getting the mushrooms to soften on the grill. Cooked them a whole lot longer than recipe calls for.  Not sure what the secret is... All that said, will definitely make them again ??

I added a pinch of cayenne pepper to help with the zing of the mayo but the Vegetarians loved it while the rest of us had burgers

Live in a Senior appartment so didnt have access to a grill. 
I put olive oil in a skillet and cooked the portabella that way. 
Husband even loved it.

Used a cast iron stovetop grill and added some spinach, which was also heated beside the P-burger

Awesome!!  Followed the recipe, but left off the bun.  So easy for hot summer nights when no one wants to cook.  Did marinate the mushrooms for about an hour before grilling them.

I used this recipe, but I only made 2 extra large mushrooms since I'm the only fan.  I used 1/2 tsp. dried basil because that's what I had on hand, and I made it on my stove top grill pan.  Since I'm doing the keto diet, I put one atop a low carb fajita with the mayo, tomato, and lettuce and ate it like an open-faced sandwich, sloppy but all the flavors were there.  I plan to use the leftover marinade and mayo with some leftover sliced steak on a fajita.  I will make this again.

We LOVED this “burger!”  My husband has never had a portobello mushroom burger so he wasn’t very excited for the menu tonight but absolutely loved the result. We followed the recipe exactly except we never flipped the mushroom or put gill-side down. Instead; we grilled a little longer and not over direct heat. This left the juice/marinade remain on the mushroom while grilling. We did toast the buns and added a slice of provolone over the mushrooms during the last minute of cooking to melt. With the Basil Mayo, tomato, lettuce…yum!!! Do not put onto buns until ready to eat or your buns will get a little soggy; which I didn’t mind but I could see impact to presentation &amp; texture. Absolutely awesome and already planning to make again THIS WEEK!! Thank you!!!

grilled portobello with basil mayonnaise sandwich

Prep Time: 10 minutes

Cook Time: 10 minutes

Total: 25 minutes

Servings: 6

Author : Rotorwife

Ingredients

Instructions

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