Preheat oven to 350 degrees.
Spray the bottom and sides of a 9-inch square baking dish with cooking oil spray.
Wash and peel the apples. Cut them into thin slices.
Spread the apple slices evenly over the bottom of the baking dish.
In a small bowl, use a fork to mix the oats, brown sugar and cinnamon.
Sprinkle the oats mixture evenly over the apples in the baking dish.
Lightly pour the apple juice over the oats mixture.
Cover the dish with foil and bake for 20-30 minutes until apples are just starting to soften.
Uncover and bake for another 15-20 minutes until apples are soft.