- Preheat oven to 350°F. Line an 8×8-inch pan with parchment paper or foil and grease lightly.
- In large bowl, combine all of the ingredients except for the apple and the caramel sauce. Stir until combined.
- Reserve 1 cup of crumb mixture for the topping. Press remaining crumb mixture evenly into the bottom of greased pan. Bake at 350°F for 10 minutes.
- Remove partially baked crust from the oven. Spread caramel evenly over the crust and then add the apples. Top with remaining crumb mixture.
- Return to oven and bake for another 30 minutes or until bubbling and lightly browned. Let cool completely before cutting into 16 squares.