Oil 9 x 13 inch pan. Mix until crumbly, flour, oatmeal, sugar, cinnamon and melted butter. Press half of crunch into oiled pan. Cover crumbs with diced rhubarb. Combine sugar, cornstarch, water ... Serve with ice cream.
Ingredients: 10 (cinnamon .. cornstarch .. flour .. oatmeal .. rhubarb ...)