Preheat the oven to . Lightly spray a 9x13-inch baking dish with nonstick spray.
Whisk together the applesauce, sugar and unsweetened cocoa poweder.
Use the whisk to beat in the egg and liquid egg whites.
Whisk in the orange zest, baking powder, vanilla extract and salt.
Juice the orange you just zested and stir the juice into the mixture.
Stir in the milk
Stir in the oats.
Cut the chocolate-orange bar into small pieces. I used a Lindt Intense Orange dark chocolate bar. Pour the batter into the prepared baking dish.
Bake at for about 45 minutes at 375 °F. The oatmeal is done when a toothpick or knife inserted into the center comes out clean.