Preheat your oven to 350°F (175°C) so it’s fully hot when the oatmeal goes in. Lightly grease an 8×8-inch baking dish or line it with parchment paper, making sure the sides are covered so the baked oatmeal doesn’t stick and slices come out cleanly.

Place the ripe bananas in a large mixing bowl and mash them with a fork or potato masher until mostly smooth. A few small lumps are fine and add texture, but the bananas should be soft and well broken down to evenly sweeten the oatmeal.

Add the yogurt, eggs, milk, vanilla extract, and salt to the mashed bananas. Whisk everything together until the mixture looks smooth and well combined, with no streaks of egg or yogurt remaining.

Add the oats, protein powder, cinnamon, and baking powder to the bowl. Stir gently until everything is just combined and the oats are evenly coated. Avoid overmixing, as this can make the baked oatmeal dense instead of soft.

Pour the oatmeal mixture into the prepared baking dish and use a spatula to spread it out evenly. Smooth the top so it bakes uniformly and doesn’t rise unevenly in the oven.

Place the dish in the center of the oven and bake until the oatmeal is set in the middle and lightly golden on top. The edges should look firm, and a toothpick inserted into the center should come out mostly clean.

Remove the baked oatmeal from the oven and let it cool completely in the dish. Cooling allows it to firm up and makes slicing much easier, giving you clean, neat portions for serving or meal prep.