Preheat the oven to 350°F. Lightly grease a 9×13-inch baking dish with nonstick spray.
In a large bowl, whisk together the milk, eggs, vanilla extract, mashed banana, peanut butter, and maple syrup until smooth and fully combined.
Stir in the oats, salt, peanut butter powder, and protein powder. Whisk or stir well until no visible clumps remain and the mixture is evenly combined.
Pour the oatmeal mixture into the prepared baking dish and spread evenly. Sprinkle chocolate chips on top.
Bake for 35–40 minutes, until the center is set and the edges are lightly golden and bubbling.
Transfer the pan to a wire rack and let cool for 5–10 minutes before slicing.
Optional drizzle: Stir the peanut butter with 1 teaspoon of melted coconut oil until smooth. In a separate bowl, microwave the chocolate chips with the remaining ¼ teaspoon coconut oil in 20-second bursts, stirring between each, until melted and smooth. Drizzle both over the warm baked oatmeal and serve.
