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.
Slice rhubarb stalks in half lengthwise and then cut them into 1/2-inch pieces (you’ll want about 3 cups of chopped rhubarb).
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.
*You can use frozen strawberries (or a mixture of berries) for this recipe. No need to thaw them.Variations:
Rhubarb crisp without strawberries: Double the amount of rhubarb, or substitute a different fruit.
Apple rhubarb crisp: Instead of strawberries, substitute 1 pound of peeled and sliced apples.
Low sugar: cut the sugar in half or substitute a sweetener.
Vegan/dairy-free: substitute vegan butter.
Gluten-free: use gluten free oats and flour.
Make ahead instructions: Prepare the filling 1 day ahead of time. Prepare the oat crumble when ready to bake.To freeze before baking: Prepare the filling, cover well and freeze for 1-2 months. Allow to thaw in the refrigerator overnight before baking. To freeze after baking: Bake as directed and allow the crisp to cool completely. Cover tightly with a double layer of aluminum foil and freeze for 1-2 months. Thaw overnight in the refrigerator, then warm in the oven at 350 degrees F or scoop individual portions and reheat in the microwave.