1. Heat the oven to 425 degrees.
2. Lightly grease an 8- or 9-inch-square glass pan. Pour fruit into the pan
3.In a small bowl, combine oatmeal, flour, nuts, and melted butter. Add the optional tablespoon of sugar if desired, and stir to combine well and until the topping clumps together. Sprinkle over the fruit.
4. Bake 15 minutes or until golden brown (longer if you have doubled or tripled the recipe). Remove from the oven and serve warm on its own or with sweetened whipped cream or ice cream.
5. Remove from the oven when the topping is golden brown and serve warm on its own or with sweetened whipped cream or ice cream.