Preheat oven to 350F and grease a 9-inch square baking dish with extra butter or oil.
Combine the dry ingredients in a large mixing bowl: oats, cocoa powder, baking powder, and salt.
To the oat mixture, add milk, eggs, melted butter or coconut oil, vanilla extract, and sweetener of choice (honey or maple syrup). Whisk to combine all the ingredients.
Let the oatmeal rest for 5 minutes on the counter. This rest period allows the oats to absorb the liquids.
Pour the oat mixture into the prepared baking pan.
(Optional) Sprinkle the top of the oatmeal with 2 tablespoons chocolate chips.
Bake for 30 minutes at 350F, or until the center is firm.
