3 tbsp. cornstarch
3 c. chopped rhubarb
1 1/2 c. sugar
1 tsp. vanilla extract
1 1/2 c. oats
1 1/2 c. flour
1 c. packed brown sugar
1/2 tsp. baking soda
1 c. shortening
1/2 c. chopped nuts (optional)

Dissolve cornstarch in 1/4 cup cold water in saucepan. Add rhubarb, sugar, and vanilla. Cook over medium heat until thickened, stirring occasionally.

Combine remaining ingredients in bowl; mix until crumbly. Pat 3/4 of the flour mixture into greased 9x13 inch baking pan. Top with rhubarb mixture. Sprinkle with remaining crumbs. Bake at 375 degrees for 30 minutes. Cool. Cut into bars.