I used the same basic recipe as The Best Apple Crisp in the World, but scaled down to make only six servings.
3 c. sliced rhubarb 1/2 c. brown sugar
3/4 c. sugar 1/2 c. oats
1/2 c. flour, divided 1/4 c. butter
1 tsp. cinnamon
Combine rhubarb, sugar and 1/4 c. flour in a bowl. Set aside. In a separate bowl, mix remaining 1/4 c. flour, cinnamon, brown sugar and oats. Add butter to oat mixture and cut in until it looks like course crumbs. Butter a 8" square baking pan. Put rhubarb mixture in pan, then spread oat mixture evenly over the top. Bake at 350° for approximately 30 minutes, or until top is crisp and golden brown.