Rhubarb Cobbler

1 cup flour
3/4 cup oatmeal
1 teaspoon cinnamon
1 cup brown sugar
1/2 cup butter, melted
1 cup sugar
1 cup water
3 tablespoons corn starch
1 teaspoon vanilla
4 cups sliced rhubarb

Combine flour, oatmeal, cinnamon, brown sugar and butter. Press half of the mixture into an 8 x 8-inch pan. Cook 1 cup sugar, water, corn starch and vanilla until very thick. Add rhubarb and mix thoroughly. Spread into cake pan and top with remaining oatmeal mixture. Bake at 350°F for 1 hour. Serve warm or cold. Delicious topped with vanilla ice cream.