Preheat oven to 375 degrees F.
Mix topping ingredients. Stir with a fork to make a crumbly mixture.
Mix rhubarb filling ingredients. Stir to mix well.
Put rhubarb mixture into a lightly greased 8 x 8 x 2 inch baking dish.
Sprinkle topping evenly over filling.
Bake, uncovered, for 35 minutes.
Serve warm with whipped cream or ice cream.