Preheat your oven to 350°F (175°C).

Peel and slice about 6 large peaches into 1/2-inch thick slices.

In a medium mixing bowl, combine the sliced peaches with 1/2 cup granulated sugar, 1/3 cup brown sugar, 1 tablespoon lemon juice, 1 teaspoon ground cinnamon, 1/4 teaspoon nutmeg (if using), and 2 tablespoons all-purpose flour. Gently toss to coat evenly without making the peaches mushy.

Transfer the peach mixture to an 8×8 inch baking dish, spreading into an even layer.

In a large bowl, combine 1 cup rolled oats, 1/2 cup cold cubed unsalted butter, a pinch of salt, 1/3 cup brown sugar, and 1 teaspoon vanilla extract.

Using your fingers or a pastry cutter, work the butter into the oats until the mixture resembles coarse crumbs with some pea-sized pieces.

Evenly sprinkle the oat crumble topping over the peaches.

Bake for 35-40 minutes until the topping is golden brown and crisp and the peach juices are bubbling around the edges.

Tent with foil if the topping browns too quickly.

Let the crisp cool slightly for about 10 minutes before serving to thicken the filling.