Preheat oven to 375 degrees F.

Crumble Topping: In a medium size bowl, combine the oat crumble topping ingredients with a fork or pastry blender until it resembles small crumbs. Refrigerate while you prepare the rhubarb filling.

Chop Rhubarb: Slice rhubarb stalks in half lengthwise and then cut them into 1/2-inch pieces (you’ll want about 3 cups of chopped rhubarb).

Assemble: In large bowl, combine rhubarb, strawberries, sugar, vanilla, zest, juice and cornstarch. Pour into 8 or 9’’ square baking dish (or similar size). If you use a shallow baking dish place it on top of a foil-lined baking sheet to catch any spills. Sprinkle crumble topping evenly on top.

Bake for about 35 minutes or until the topping is golden and fruit is bubbling.