Preheat your oven to 350°F. Grease a prepared baking dish lightly with butter or nonstick spray. Either an 8x8 or 9x13 baking dish work perfectly; just keep in mind the larger the dish the quicker it'll bake through.
Spread apple pie filling evenly into the pan.
In a large mixing bowl, combine flour, old-fashioned oats, brown sugar, cinnamon, and salt. Stir until the dry ingredients are blended. Pour in the melted butter and mix until a crumbly topping forms.
Sprinkle the oat topping evenly over the top of the apples. You want to cover all of the apple filling.
Place the dish in the oven, middle position. Bake for 30-35 minutes or until bubbly and golden.
Let the crisp cool for 10 minutes. Serve warm with a scoop of ice cream or fresh homemade whipped cream.