Prepare the peaches: Preheat oven to 375degrees F. Place sliced peaches in a large mixing bowl. Add brown sugar, cornstarch, salt, and cinnamon. Stir gently until peaches are coated.
Make the topping: In another bowl, combine flour, oats, brown sugar, salt and butter. Use a pastry blender, forks or your hands to combine mixture into small crumbles.
Assemble: Pour the peach mixture into a greased 9 inch baking dish. Sprinkle the topping all over the peaches.
Bake: Bake for 35 to 40 minutes or until topping is golden brown and peaches are bubbling.
Serve: Let cool slightly before serving. Best enjoyed warm with vanilla ice cream or whipped cream.