Step 1

Preheat oven to 350 degrees F (175 degrees C). Grease an 8-inch square baking pan.

Step 2

Mix oats, brown sugar, whole wheat flour, cocoa powder, all-purpose flour, and baking powder together in a large bowl; mash in banana. Stir in eggs, butter, milk, applesauce, and vanilla extract; mix thoroughly until batter is smooth. Pour into the baking pan. Sprinkle chocolate chips on top.

Step 3

Bake in the preheated oven until a toothpick inserted into the center comes out clean, 40 to 45 minutes.