Preheat oven to 375°F (190°C). Grease a 9x9-inch baking dish.
In a large bowl, combine strawberries, rhubarb, sugar, and cornstarch. Spread evenly into the dish.
In another bowl, mix oats, flour, brown sugar, cinnamon, and salt. Stir in melted butter until crumbly.
Sprinkle topping evenly over fruit filling.
Bake for 35–40 minutes until the topping is golden and the filling is bubbling.
Cool for 15 minutes before serving. Serve warm, plain or with vanilla ice cream.