Preheat oven to 350°F. Line an 8x8-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.