1 cup light brown sugar, firmly packed
1 cup all-purpose flour
3/4 cup quick cooking rolled oats
1/2 cup melted butter
1 teaspoon cinnamon
4 cups sliced rhubarb
1 cup granulated sugar
2 tablespoons cornstarch
1 cup water
1 teaspoon vanilla
In mixing bowl, combine brown sugar, flour, oats, butter and cinnamon; mix together until crumbly. Press half of the brown sugar and oats mixture into a buttered 8-inch square baking dish. Top with the sliced rhubarb.
In a saucepan combine 1 cup granulated sugar, cornstarch, and the 1 cup of water and vanilla. Cook together until clear, then pour over rhubarb.
Top rhubarb with remaining crumb mixture and bake at 350° for 45 to 55 minutes.