Frozen strawberries, blueberries, and blackberries are perfect in this simple baked crisp. Use equal parts frozen berries and pitted cherries for delicious results, too.
Preheat the oven to 375 degrees.
In a large bowl, gently toss together the berries, sugar, and flour then transfer to an 8-inch baking dish. Set aside.
In a medium-sized bowl, toss together the granola and butter then scatter over the berries in the dish. Bake until the top is golden brown and berries and their juices are bubbly, about 30 minutes. Let cool, then spoon into dishes, and serve with yogurt or ice cream on top, if using.