Preheat oven to 350 degrees F.
Combine the oats, brown sugar, flour, cinnamon and salt in a medium-sized bowl. Cut in butter until the mixture resembles coarse crumbles; set aside.
Peel, core and slice apples to make 5-6 cups. Toss fruit with 2 to 3 tablespoons of sugar. Add fruit to a baking dish (10"x6"x2"), or in a pie plate.
Sprinkle crumb mixture over the top.
Bake in a 350 degree oven for 40 to 45 minutes. Remove and let cool.