1 c. flour
3/4 c. oatmeal
1 c. brown sugar
1/2 c. melted butter
1 tsp. cinnamon

Mix and spread 2/3 of this crumble mixture 1/2 inch thick in a 9 x 9 inch pan. Add 4 cups chopped rhubarb onto the crumble mixture. In a pot, mix 1 cup sugar and 2 tablespoons cornstarch. Add 1 cup water and 1 teaspoon vanilla. Heat until boiling, and mixture is thick. Pour over rhubarb, then cover with the remaining 1/3 of the crumble mixture. Bake 1 hour at 350 degrees.