Preheat the oven to 350 F. In a medium bowl, whisk together flour, sugar, cocoa powder, salt, and baking soda. Add in eggs, melted butter, and vanilla extract until smooth.
In a medium bowl, whisk together flour, quick oats, salt, and baking soda. In a large bowl, combine butter, peanut butter, granulated sugar, and brown sugar until fluffy. Add in egg and vanilla extract, and mix until it is smooth.
Add in the flour mixture, and mix until it is fully combined. Fold in chocolate chips and M&Ms.
Pour the brownie batter into a greased 8-inch square baking dish. Top evenly with the monster cookie dough. Bake for 25-30 minutes.
