Preheat oven to 350 degrees F. Coat an 8x8 baking dish with cooking spray and set aside.
In one bowl, combine oats, brown sugar, cinnamon, baking powder, and salt. In another bowl, whisk together milk, applesauce, melted butter, egg, and vanilla. Pour wet ingredients over dry ingredients and stir until combined. Gently stir in diced apples and raisins.
Pour oatmeal into prepared baking dish. Bake for 20-25 minutes or until oatmeal is golden brown and set.
Best if served warm – if needed, reheat in the microwave for 1:30 – 2:00 minutes. Serve with a splash of milk and some fresh fruit. Enjoy!