In a large bowl, mix the melted and cooled butter, brown sugar, sugar, vanilla, peanut butter, and eggs using a whisk.
1 cup butter, 3/4 cups light brown sugar, 1/2 cup white sugar, 3/4 cups peanut butter, 1 tbsp vanilla, 2 eggs
Mix in the flour, baking soda, baking powder, salt, and oats. Use a rubber spatula to mix until just combined. Add in the mini chocolate chips, M&M's, and mini M&M'S.
2 1/3 cups all-purpose flour, 1 cup quick oats, 1/2 tsp baking soda, 1/4 tsp baking powder, 1/4 tsp salt
Preheat the oven to 350°F. Line two cookie sheets with parchment paper. Bake 6 cookies at a time for 12-15 minutes or until the edges are a light golden brown. The middle will still look soft, but will continue to bake from the warmth of the pan after it's out of the oven!
Cool the cookies on the baking tray for 10 minutes and then transfer to a cooling rack. Enjoy!