In a large bowl, combine cherries, 1 1/2 cups white sugar, and 4 tablespoons flour. Pour into 9x13 inch baking dish. In a medium bowl, combine 1 1/2 cups flour, oats, and brown sugar. Cut in butter and shortening until crumbly. Sprinkle over cherries.
Bake in preheated oven for 45 to 50 minutes, or until topping is golden brown.