Preheat your oven to 375°F. Grease a 3-quart baking dish (like a 12x8x2.5 or a 13x9). Set it aside.

In a mixing bowl, combine the flour, oats, brown sugar, and salt, breaking up any clumps of brown sugar with your fingers. Add the butter and mix it in with your fingers or a pastry cutter until the mixture forms pea-sized crumbles. Pop this in the fridge while you prep the filling.

In a large mixing bowl, toss together the strawberries, rhubarb, orange juice, and orange zest. In a separate bowl, whisk together the granulated sugar and cornstarch, then add this to the fruit mixture. Toss everything until the fruit is evenly coated.

Pour the fruit mixture into your prepared baking dish and spread it out evenly. Take the crumble mixture from the fridge and sprinkle it evenly over the top of the fruit.

Bake in the preheated oven for 30 to 40 minutes, until the juices are bubbling and the top is golden brown. Serve warm with a scoop of vanilla ice cream if you like.