Preheat your oven to 350°F (175°C). Prepare your baking dish.

In a large mixing bowl, combine blueberries, sliced peaches, lemon juice, lemon zest, vanilla extract, granulated sugar, and flour. Toss until coated and let it rest for 5-10 minutes.

In another bowl, mix flour, oats, brown sugar, salt, and cinnamon. Rub in cold butter until it resembles coarse crumbs.

Spread the fruit filling in the greased baking dish and sprinkle the crumble topping evenly over the fruit.

Bake for 40-45 minutes until the topping is golden brown and juices are bubbling.

Let it cool for about 10 minutes before serving warm, ideally with vanilla ice cream or whipped cream.