Preheat the oven to 350°F (175°C).

In a mixing bowl, combine the pitted cherries, granulated sugar, cornstarch, and vanilla extract. Toss until the cherries are well coated.

Pour the cherry mixture into a greased baking dish.

In another bowl, mix together the rolled oats, flour, brown sugar, melted butter, and cinnamon until crumbly.

Sprinkle the topping evenly over the cherry filling in the baking dish.

Bake in the preheated oven for 30 minutes, or until the topping is golden brown and the cherries are bubbling.

Remove from the oven and let cool slightly before serving.