Preheat the oven to 350°F (175°C). In a mixing bowl, combine blueberries, sliced peaches, granulated sugar, lemon juice, and cornstarch. Toss to coat the fruit evenly.

In another mixing bowl, combine oats, flour, brown sugar, almond slivers, melted butter, and cinnamon. Mix until crumbly.

Spread the fruit mixture evenly in a baking dish. Sprinkle the topping mixture over the fruit. Bake in the preheated oven for 30 minutes or until the topping is golden brown and the fruit is bubbly.

Remove from the oven and let cool for a few minutes before serving. Enjoy warm, optionally with vanilla ice cream.