Preheat oven to 350 degrees. Add rhubarb and strawberries to a 9 inch baking pan. Make sure you have enough space for the crumble on top! Add maple syrup and lemon juice, tossing to combine.
Prepare crumble topping: in a medium bowl, combine brown sugar, oats, butter, flour and salt. Mix together until crumbly. Top rhubarb and strawberries with crumble.
Bake for 30-40 minutes, until bubbling and fragrant. Allow to cool slightly before serving with vanilla ice cream.