Preheat your oven to 350°F (175°C) and grease a 9×13-inch baking dish.

Melt the butter in a saucepan over low heat. Stir in granulated sugar and brown sugar until well combined.

Let the mixture cool slightly before whisking in eggs one at a time and adding vanilla extract.

In another bowl, sift together cocoa powder, flour, baking powder, and salt. Gradually add to the wet mixture until just combined.

Fold in oats, M&M's candies, and chocolate chips.

Pour the batter into the prepared dish and bake for 25-30 minutes or until a toothpick comes out with moist crumbs.