Preheat oven to 375° and place rack in the center of the oven. Butter or spray with nonstick cooking spray a 2-½ quart casserole or oval dish, or a 10-inch deep pie plate. Set aside.
For topping: combine the flour, sugar, oats and nuts in a large bowl. Cut the butter into small pieces and blend the flour mixture with a pastry blender. The mixture should be crumbly and about the size of peas. Set aside while you prepare the filling.
For filling: In a large bowl combine the sugars, cornstarch, cinnamon and salt. Peel core and slice the apples and pears and toss them along with the cranberries, in the sugar mixture. Once combined, transfer to the prepared pan. Spread the topping evenly over filling.
Bake 35-45 minutes or until the topping is golden brown and crisp. Remove from oven and place on a wire rack to cool for at least 15 minutes. Serve with whipped cream or vanilla ice cream. Refrigerate leftovers and reheat before serving