Preheat the oven to 350 degrees F / 175 C.
In a large mixing bowl combine flour, baking soda, salt, and oats altogether.
In another bowl (or a kitchen mixer) cream butter, peanut butter, white sugar, and brown sugar until well combined. Add vanilla, egg, and egg yolk and mix well.
Slowly add the flour mixture a little bit at a time, until all is added.
With a spatula add mini chocolate chips and M&Ms and stir until well combined.
Grease an 8x10 baking dish with cooking spray. Add the mixture and spread out until even.
Bake until golden brown about 15 to 18 minutes. Time depends on your oven.
