01 - Preheat oven to 375°F. Lightly grease a 9-inch baking dish with butter or cooking spray.
02 - Combine strawberries, rhubarb, granulated sugar, cornstarch, vanilla extract, and lemon juice in a large bowl. Toss until fruit is evenly coated. Transfer mixture to the prepared baking dish.
03 - Whisk together flour, oats, brown sugar, cinnamon, and salt in a separate bowl. Add cold butter cubes and work into the dry ingredients using your fingertips or a pastry blender until coarse crumbs form.
04 - Sprinkle the crumble topping evenly over the fruit mixture, covering completely.
05 - Bake for 35-40 minutes until the topping is golden brown and the fruit filling is bubbling around the edges.
06 - Let cool for 10-15 minutes to allow the filling to set. Spoon into bowls and top each serving with a scoop of vanilla ice cream.