Preheat the oven to 375 F.
Grease a 9x9 baking dish.
Combine apples, flour, sugar, salt, and water and toss together, then put in the baking dish.
With pastry blender, cut the butter into the oats, salt and brown sugar.
Sprinkle on top of the apples, then bake 35 minutes, until the apples are soft.