Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking dish with unsalted butter.
In a large bowl, combine the sliced peaches, lemon juice, brown sugar, cornstarch, vanilla extract, and cinnamon. Gently toss until the peaches are well coated.
Pour the peach mixture into the prepared baking dish, spreading it evenly.
In another bowl, create the crumble topping by mixing together the flour, rolled oats, brown sugar, salt, and nutmeg.
Add the chilled, cubed butter to the dry mixture. Using your fingertips or a pastry cutter, work the butter into the mixture until it resembles coarse crumbs.
Sprinkle the crumble topping evenly over the peach mixture in the baking dish.
Bake in the preheated oven for 30-35 minutes or until the topping is golden brown and the peaches are bubbling.
Once cooked, remove from the oven and allow it to cool for about 10 minutes before serving.
Notes
Serve warm in bowls, topped with a scoop of vanilla ice cream and a sprinkle of fresh mint for an extra pop of color!