Heat oven to 425 degrees. Line 9-inch pie plate with crust. Roll out top crust. Mix all ingredients except rhubarb, strawberries, and butter.
Place half of rhubarb, half of strawberries in the pie plate; sprinkle with half of the sugar mixture. Repeat, then dot with butter. Cover with top crust. Bake 40-50 minutes. Serve warm or cold.