Step 1

Preheat oven to 350°. Line cookie sheets with parchment paper, use a silpat liner, or spray with cooking spray.

Step 2

In a large bowl (or bowl of a stand mixer) cream together the butter, brown sugar, and peanut butter until light and fluffy, about 1-2 minutes.

Step 3

Mix in the egg and vanilla, scraping down the sides of the bowl as needed.

Step 4

In a separate bowl, add the flour, baking soda, cornstarch, baking powder, and salt and whisk to combine.

Step 5

With the mixer on low speed, slowly add the flour mixture to the wet ingredients and mix until just combined.

Step 6

Add the oats, chocolate chips, and M&M candies. Mix on low speed just until dough is combined.

Step 7

Use a medium cookie scoop, or about 2 tablespoons cookie dough, and place on the baking sheets. They should look like golf balls.

Step 8

Bake the cookies for 7-9 minutes until the edges are just starting to brown and the top still looks slightly undercooked.

Step 9

Remove from the oven and cool for 5 minutes on the baking sheet before moving them to a wire rack to cool completely.

Step 10

** These cookies don't spread much after baking. If you gently press additional m&m's onto the tops of each cookie that will help flatten the cookie to more of a "cookie shape". You can also tap the hot cookie sheet against the countertop or stove top to help the cookies to fall.