Preheat the oven to 350°F (175°C).

In a mixing bowl, combine 4 cups fresh or frozen cherries, 1 cup granulated sugar, 2 tablespoons all-purpose flour, and 1 teaspoon vanilla extract; stir until the cherries are evenly coated.

Pour the cherry mixture into a greased 9x9 inch baking dish and spread it into an even layer.

In another bowl, mix 1 cup rolled oats, 1 cup brown sugar, 1 cup all-purpose flour, and 1 teaspoon ground cinnamon.

Pour 1/2 cup melted unsalted butter into the oat mixture and stir until crumbs form.

Evenly sprinkle the butter-oat topping over the cherry filling.

Bake in the preheated oven for 30 minutes or until the topping is golden brown and the filling is bubbly.

Let the dessert cool for at least 10 minutes before serving to allow the filling to set.