Step 1

Combine the grainy coarse mustard, smooth Dijon mustard, honey, extra virgin olive oil, lemon juice, and minced garlic in a 2 cup glass measuring cup.

Step 2

Remove the rosemary leaves from the stem. Finely chop them.

Step 3

Add the chopped rosemary, salt, and pepper to the measuring cup. Stir to combine well.

Step 4

Set 1/4 cup of the marinade mixture aside for basting.

Step 5

Add the marinade to a gallon sized zip top plastic bag along with the chicken.

Step 6

Seal the bag and flatten the contents, making sure that the marinade is evenly dispersed throughout the chicken.

Step 7

Place the bag, flat, on a baking sheet. Transfer to the refrigerator and marinade at least an hour, or up to overnight.

Step 8

Prepare the grill be ensuring the grates are cleaned off completely.

Step 9

Preheat the grill, with the lid closed, until the grill thermometer indicates that it has reached 400 degrees F (if you are using a gas grill, or any grill that has a built in thermometer).

Step 10

While the grill preheats, remove the chicken from the bag and place on a plate. It is not necessary to rinse the chicken. Season with additional salt and pepper if desired.

Step 11

Place the chicken tenderloins on the preheated grill and close the lid. They will only need to cook for about 3-5 minutes per side.

Step 12

Flip the chicken, close the lid, and cook another 3-5 minutes.

Step 13

When the chicken is cooked through (165 degrees F internal temp), remove it from the grill and transfer it to a clean baking sheet.

Step 14

Baste, if desired, with the reserved 1/4 cup of marinade mixture (not the mixture that was in the bag with the raw chicken as this is not safe to consume).

Step 15

Let rest for 3-5 minutes, transfer to a platter, garnish with lemon slices and rosemary sprigs if desired.

Step 16

Serve.