To make the crust in a large mixing bowl add the oats, flour, turbinado sugar, baking powder, cinnamon, and melted butter.
Mix until combined and distribute ¾ of the mixture in a brownie pan with the help of your hands.
To make the cream cheese filling, in a large mixing bowl mix the cream cheese, sugar, egg, and vanilla together and spread the cream cheese filling all over the crust.
To make the apple mixture, in a bowl combine the sliced apples, flour, sugar, and cinnamon and top the cream cheese mixture with the apple mixture.
Finally, top everything with the remaining crust mixture crumbling on top of the apple mixture.
Bake the apple cream cheese bars in an already heated oven at 350 F or 180 C degrees for about 25-30 minutes.