In a medium bowl, combine rhubarb, white sugar and 1/4 cup flour. Place mixture in the unbaked pie crust.
In a separate bowl, beat eggs slightly. Stir in melted butter, vanilla, and brown sugar. Blend in 1/3 cup flour, oats, and cinnamon. Spread over rhubarb layer.
Bake in preheated oven for 40 to 50 minutes, or until top is golden brown and filling is set.
Interesting Facts
Rhubarb has been used in pies since the 1700s.
This pie is a great way to use up extra rhubarb in your garden.
Rhubarb is a vegetable, but it is used as a fruit in this recipe.