Preheat your oven to 375°F (190°C) and grease a 9x13 inch baking dish with butter.

In a large mixing bowl, combine sliced peaches with granulated sugar, light brown sugar, flour, cornstarch, lemon juice, cinnamon, salt, and vanilla extract. Let sit for 10 minutes.

Pour the peach mixture into the prepared baking dish, spreading it evenly.

In a separate bowl, whisk together flour, oats, brown sugar, granulated sugar, cinnamon, and salt for the crumble topping.

Cut in cold butter until the mixture resembles coarse crumbs.

Sprinkle the crumble topping evenly over the peach mixture.

Bake for 40-45 minutes until the topping is golden brown and filling is bubbly. Tent with foil if needed.

Let cool for at least 20 minutes before serving. Enjoy warm, optionally with vanilla ice cream.