Preheat the oven to 375 °F. Lightly spray a 9x13-inch baking dish with nonstick spray.
Whisk together the applesauce, ½ cup of sugar and ⅓ cup unsweetened cocoa powder.
Use a whisk to beat in the egg and ¼ cup egg whites
Whisk in 1 teaspoon baking powder, ¼ teaspoon salt, 1 teaspoon vanilla extract and ¼ teaspoon peppermint extract.
Stir in the milk
Stir in the oats
Cut up the peppermint bark into tiny pieces and stir it into the oatmeal mixture.
Pour the oatmeal mixture into the prepared baking dish.
Bake for about 45 minutes at 375 °F . The oatmeal is done when a toothpick or knife inserted into the center comes out clean.