Preheat oven to 350 degrees and line a 9x13-inch baking dish with parchment paper.
Make crust. In a large bowl, use an electric mixer to beat butter and flour until combined well.Press evenly into bottom of the parchment paper-lined baking dish.
Bake 16 to 20 minutes. Let cool 15 minutes.
Make topping. Mix together flour, brown sugar, 2/3 cups oats, cinnamon, and salt in a large bowl.
Add butter and use your fingers to work it in.
Chop up the apples some in the apple pie filling and spread the filling over the cooled crust.
Sprinkle the topping over the apples and then sprinkle the remaining 1/4 cup oats on top.
Bake for 45 minutes. Let cool before adding glaze.
Drizzle glaze on and cut into squares.
Notes
You can use unsalted butter and add a pinch of salt.