Rhubarb Crunch (Darla Lenon' recipe posted by Chris Auger)

4 cups Rhubarb

crumbs:
1 C flour
1 C brown sugar packed
¾ C uncooked oatmeal
½ C melted butter
1 teaspoon cinnamon

sauce:
1 teaspoon vanilla
1 C sugar
1 C water
2 Tablespoons cornstarch

Mix until crumbly the crumbs ingredients. Press half of crumbs into a 9x13 greased baking dish. Put 4 cups diced rhubarb over packed crumbs. Combine the sauce ingredients, cook until thick and clear, and pour over rhubarb. Top with remaining crumbs. Bake at 350 degrees for 1 hour.