Preheat oven to 350 degrees F. Butter a 7x11-inch baking dish.
Mix together the blueberries and sliced apples in the dish. Sprinkle with brown sugar.
In another bowl, mix together the flour, sugar, baking powder, salt and beaten egg until mixture becomes crumbly. Sprinkle over the fruit.
Drizzle melted butter on top and sprinkle with cinnamon. Bake for 30 minutes until top is golden brown. Serve warm with whipped cream or vanilla ice cream.