• 1 cup all-purpose flour
• 1 cup old fashioned oats
• 1 cup packed brown sugar
• 1 teaspoon ground cinnamon
• 1/2 cup cold butter
• 4 cups diced fresh rhubarb
• 1 1/3 cups sugar
• 2 teaspoons cornstarch
• 1 cup cold water
• 1 teaspoon vanilla extract

In a large bowl, combine the first four ingredients.  Cut in butter until mixture resembles coarse crumbs.  Press half of the mixture into a greased 8″ square baking dish.  Set remaining crumb mixture aside for topping.  Sprinkle rhubarb over crust; set aside.

In a small saucepan, combine the sugar and cornstarch; gradually whisk in water until smooth.  Bring to a boil; cook and stir for two minutes or until thickened.

Remove from the heat; whisk in vanilla.  Pour over rhubarb.  Sprinkle with reserved crumb mixture.  Bake, uncovered, at 350 degrees for one hour or until bubbly and lightly browned.  Serve warm with vanilla ice cream, if desired.