Preheat oven to 350 F. Grease a 9x12 casserole, or a 2-quart casserole or soufflé dish.
Slice fruit and put it into a large bowl. Add the rest of the filling ingredients to the fruit and gently toss to incorporate peaches and flour mixture. Place fruit in the bottom of the prepared pan. Set aside.
For the topping, place all ingredients into a food processor and pulse until the mixture is crumbly and the size of peas. This can also be done with a pastry cutter. Sprinkle crumb topping mixture evenly over fruit and pat down slightly with a spatula.
Bake for about 30 minutes, or until fruit is beginning to bubble up along the sides and the topping is golden brown and getting crispy.