Lightly coat an 8×11 baking dish with nonstick cooking spray.
How To Make One Pan Baked Oatmeal?
Mash two ripe bananas in a baking dish.
Add the rolled oats on top.
Sprinkle the chia seeds on top.
Pour the milk over the other ingredients and stir to combine.
Add the frozen berries, cinnamon, and lemon zest on top and pop it in the preheated oven.
Bake in the preheated oven for about 25 minutes - you'll know it's ready when the oats have thickened, and the liquid is fully absorbed.
How to Serve One Pan Baked Oatmeal?
Once baked, serve the oatmeal hot, optionally drizzling with maple syrup.
Notes
Store any leftover oatmeal tightly covered with plastic wrap or in an airtight container for up to 4 days.
Reheat leftovers in the microwave or oven until warmed through before serving.