Preheat oven to 350 degrees.
Prepare a 13x9 baking pan with cooking spray.
Combine the flour, oats, powdered sugar, pie spice, baking powder and salt.
Using your fingers, work the butter in until you get a coarse, crumbly mixture.
Spread 3/4 of this cookie mixture into your prepared pan. Press down firmly.
Combine the filling ingredients and spread over the bottom layer.
Sprinkle the remaining dough mixture over top.
Bake for 40-45 minutes or until the top is beginning to turn a golden brown.
Cool completely on a rack in the pan and cut into squares.