Preheat oven to 350 degrees.
Peel and sliced the apples into thin slices, about 1/4" thick or less. Toss the apple slices in a bowl with the sugars and cinnamon. Once coated, spread out in a casserole dish or 9"x13" pan and let sit.
In a mixing bowl with a pastry cutter or food processor - combine the flour, oats, sugars and butter until crumbly. NOTE - If you're using a food processor, add the oats at the end, mixing them in by hand. This will allow them to stay in tact.
Pour the melted butter over the apples and then spoon the crumble topping evenly over the apples mixture.
Bake for 30-35 minutes or until topping is golden brown. Allow it to rest for for a few minutes and then serve warm with a scoop of ice cream.