Cream the peanut butter, eggs, brown sugar, granulated sugar, and vanilla in a stand mixer until just combined. Scrape the sides of the bowl to make sure all ingredients are blended.
Add the rolled oats, baking soda and salt and mix until combined.
Add in the mini M&Ms and mini chocolate chips and hand stir until completely incorporated into the dough. (The dough will be thick and wet but this is what it should look like.)
Cover the bowl of cookie dough with plastic wrap and refrigerate for at least 2 hours.
Line a baking sheet with parchment paper or a silpat.
When the dough is chilled, preheat oven to 350 degrees and remove dough from refrigerator and use a medium cookie scoop to scoop the dough into balls. No need to press the cookie dough balls down. Leave them as balls.
Bake for 8-10 minutes and edges are set. Keep remaining dough in refrigerator until ready to bake.
Allow baked cookies to cool on the baking sheet for 10 minutes and then remove to a cooling rack.