Blueberry-Rhubarb Crumble

3 cups fresh or frozen (thawed & undrained) blueberries
2 cups fresh or frozen (thawed & undrained) rhubarb cut into 1" pieces
1 1/2 cups oatmeal, uncooked
2/3 cup packed brown sugar
1/2 cup plus 2 T flour, divided
1/2 cup butter
1/2 cup white sugar
Whipped Cream

Crust:  Combine oatmeal, brown sugar, and 1/2 cup flour.  Cut butter into this mixture with a fork or pastry cutter until mixture resembles coarse crumbs.  Reserve 2/3 cup for topping.  Pat remaining crumbs into the bottom of a greased 9x9" baking pan.  Bake at 350 degrees for 15 minutes.

Filling:  Combine the two fruits, white sugar, and 2 T. flour; toss to coat well.  Spoon on the baked crust.  Sprinkle with reserved crumb mixture.  Continue baking 45-50 minutes more.  Serve warm with whipped cream.