Preheat oven to 350 degrees.
Peel, core, and slice apples and place in a large bowl.
Toss together apples, sugar, lemon juice, and cinnamon.
In a medium bowl, whisk together brown sugar, flour, rolled oats, melted butter, and salt.
Arrange apples evenly in the bottom of a 9X13 glass baking dish.
Spoon oat mixture on top of apples.
Bake for 40-45 minutes, until crumble is golden brown and apples are fork tender.