Preheat the oven to 350°F and prepare a 9-inch cake pan with parchment paper and butter.

Cream together the butter, peanut butter, brown sugar, and sugar until light and fluffy.

Add the egg and vanilla extract and mix well.

In a separate bowl, whisk together the flour, baking soda, baking powder, and salt.

Gradually add dry ingredients to the wet mixture and mix until combined.

Stir in the oats, M&Ms, and chocolate chips.

Pour the batter into the prepared cake pan and press evenly.

Bake for 16 minutes or until edges are golden. Cool completely before serving.