Spray a 15x10x1-inch pan with nonstick cooking spray and set aside.
For the pie crust, combine the flour and salt in a large bowl. Use a pastry blender to cut in the shortening until it resembles coarse crumbs about the size of peas. Sprinkle 1 tablespoon of cold water over the mixture and toss with a fork. Repeat with 1 tablespoon of water at a time, until moistened and the dough begins to come together. Use your hands to form the dough into a ball.
Preheat oven to 375°F/190°C
On a lightly floured surface, roll the dough into a 19x13-inch rectangle, a few inches larger than the prepared pan. Gently roll the crust dough around the rolling pin and unroll it into the pan. Lift the edges and press the dough into the pan, without stretching the dough. Trim edges of dough to about 1/2 inch beyond the edge of the pan. Fold the dough edge and flute as desired. Place in refrigerator.
In an extra large bowl, combine the sugar, flour and cinnamon for the apple filling. Then add the apple slices and toss to coat.
In a medium bowl, stir together the quick oats, brown sugar, and flour for the topping. Using a pastry blender, cut in the butter until the topping resembles coarse crumbs.
Remove the crust from the refrigerator and fill it with the apple mixture. Then sprinkle the topping evenly over the apples. Bake for 40-45 minutes, or until apples are tender. If needed, cover with foil for the last 5-10 minutes to prevent it from browning too quickly.
Let cool slightly. Drizzle caramel sauce over the top. Cut into squares and serve.