Crust:
2 cups flour
1 ½ cups brown sugar
1 ½ cups oats
2 tsp cinnamon
10 TB butter, melted
Filling:
2 lbs. diced rhubarb (about 8 cups)
1 ½ cups granulated sugar
¼ cup cornstarch
2 cups water
2 tsp vanilla
Combine all crust ingredients and spread half of mixture in a greased 13 x 9 pan. Top with rhubarb. Combine sugar, cornstarch, and water in medium saucepan. Heat to boiling, stirring occassionally. Add vanilla and pour over rhubarb. Top with remaining crust. Bake at 350° for about 1 hour, until browned and bubbling.