Pre-heat the oven to 375 °F
Spray a 13x9-inch baking dish with nonstick spray
Whisk together the mashed bananas, egg, egg whites, sugar, vanilla extract, baking powder and salt
Stir in the milk
Stir in the uncooked oats
Stir in the strawberries
Pour into the baking dish and bake for about 45 minutes, or until a toothpick or knife inserted into the center of the oatmeal comes out clean. If you're using frozen strawberries, you might need to bake it a little longer (about one hour), so keep your eyes on it!