In a large bowl, combine the flour, oats, sugar, cinnamon and salt. Use a pastry cutter or your fingers to cut in butter until mixture forms coarse crumbs. Sprinkle the topping evenly over the fruit mixture and bake for 45-50 minutes, until the topping is browned and set and the juices are bubbly. Transfer to a wire rack and let cool for 10 minutes. Serve warm (or room temperature) with vanilla ice cream on top. Enjoy!