Preheat oven to 350. Lightly spray a 9x13 baking dish with non-stick cooking spray.
In a large sauce pan, melt butter over medium heat. Stir in sugar until sugar starts to dissolve. Remove pan from heat. Add eggs one at a time stirring after each addition. Stir in vanilla.
Mix in baking cocoa and beat until well-blended. Add baking powder, salt, and flour. Stir until well-combined. Pour batter into prepared baking dish.
Sprinkle with peanut butter and chocolate chips.
Stir together sweetened condensed milk and peanut butter. Pour over the top of the chips.
Sprinkle with M&M candies.
Bake for 20-30 minutes or until edges of bars start to turn brown. Allow to cool completely before cutting into bars.
Recipe by A Kitchen Addiction at https://www.a-kitchen-addiction.com/peanut-butter-brownie-magic-bars-oxogoodbrownie/