Step 1

In a medium bowl, whisk the oats, baking soda, and salt together until combined. Set aside.

Step 2

In a large bowl, whisk the melted butter, brown sugar, eggs, and vanilla together until combined. Whisk in the peanut butter.

Step 3

Pour the dry ingredients into the bowl with the wet ingredients and mix with a silicone spatula until combined. (Takes some arm muscle!) Fold in the M&Ms and chocolate chips. The dough will be sticky and gooey.

Step 4

Cover the cookie dough tightly and chill in the refrigerator for at least 30 minutes and up to 3 days.

Step 5

Preheat oven to 350°F (177°C). Line large baking sheets with parchment paper or silicone baking mats.

Step 6

Scoop the dough, a heaping 2 Tablespoons (45g) each, and place the mounds of cookie dough about 3 inches apart on the prepared baking sheets. (A medium cookie scoop helps with the sticky dough, but make sure it is a heaping scoop to get you 2 Tablespoons (45g) of dough.)

Step 7

Bake until the edges are set and golden brown, about 12–15 minutes. The cookies will still look soft in the centers.

Step 8

Cool cookies for 10 minutes on the baking sheet. During this time, I like to press a few more chocolate chips or M&M’s into the tops of the warm cookies. (This is optional and only for looks.) Transfer to wire rack to cool completely.

Step 9

Cover leftover cookies tightly and store at room temperature for up to 1 week.