Preheat your oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish.

In a large mixing bowl, combine the sliced peaches, granulated sugar, cornstarch, vanilla extract, and 1 teaspoon of ground cinnamon. Toss until the peaches are evenly coated.

Transfer the peach mixture to the prepared baking dish, spreading it out evenly.

In a separate bowl, prepare the topping by mixing together the rolled oats, flour, brown sugar, 1 teaspoon of ground cinnamon, and salt. Stir to combine.

Pour the melted butter into the oat mixture and stir until the topping becomes crumbly and evenly moistened.

Sprinkle the topping evenly over the peach mixture in the baking dish.

Bake in the preheated oven for 35-40 minutes, or until the topping is golden brown and the peach filling is bubbling.

Allow the peach crisp to cool for about 10 minutes before serving. Serve warm, optionally with a scoop of vanilla ice cream or whipped cream.