This recipe is excellent and i tried it a couple of times myself, too.
Shifted flour 1 cup Brown sugar 1 cup Melted butter 1/2 cup Cinnamon 2 tsp Oatmeal 3/4 cup Diced Rhubarb 4 cups Sugar 1 cup cornstarch 2 tsp Water 1 cup Vanilla extra 1 tsp
Mix flour, brown sugar, butter, cinnamon, salt and oatmeal until crumbly. Press 1/2 of crumbs into a buttered 9" square pan, cover with diced apples (or rhubarb). Combine sugar, cornstarch, water and vanilla. Cook until thick and pour over fruit. Top with remaining crumbs. Bake in moderate oven, 350 degrees 1 hour. Cut in squares and top with whipped cream if desired.