Preheat your oven to 350 degrees F. Line two baking sheets with parchment paper or a silicone mat and set aside.
In a large mixing bowl, beat the peanut butter, brown sugar, sugar, and butter until fluffy and smooth, about 2 minutes.
Mix in the eggs and vanilla until combined. Scrape the sides of the bowl as needed. Mix in the oats and baking soda until fully incorporated.
Fold in the chocolate chips and M&Ms by hand until evenly distributed throughout the cookie dough.
Using a cookie scoop, drop 2 tablespoons scoops of dough onto the prepared baking sheets. Add a few extra M&Ms on top of each dough ball, if desired.
Bake for 10 minutes until the cookies are set and the edges are golden.
Remove the cookies from the oven and allow them to cool on the baking sheet for 5 minutes. Then transfer the cookies to a wire rack to cool completely. Store in an airtight container.
Notes
The cookies won’t appear done after 10 minutes, but they are and will set up nicely. You don’t want to overbake them!
You can substitute 1/2 cup of Biscoff cookie spread for 1/2 cup of peanut butter if you want to change up the flavor.
You can use any holiday-themed M&M's mix to easily switch up the theme of these cookies.