Preheat the oven to 350°F (175°C). In a large bowl, combine the sliced peaches with sugar, cinnamon, nutmeg, and lemon juice. Toss gently until the peaches are coated and set aside to macerate slightly.
In a separate bowl, mix together oats, flour, and brown sugar. Add the cold butter pieces and use your fingertips or a pastry cutter to work the butter into the dry ingredients until the mixture resembles coarse crumbs.
Stir the bourbon into the crumble mixture, blending it just until incorporated. This adds a subtle depth and aroma to the topping.
Pour the peach mixture into a greased baking dish, spreading it evenly with a spatula. Sprinkle the streusel topping over the peaches, covering them completely.
Bake in the preheated oven for about 40 minutes, or until the topping is golden brown and bubbling at the edges. The aroma of cinnamon, peaches, and baked butter will fill your kitchen.
Remove from the oven and let the crisp cool slightly before serving. The topping will be crisp and caramelized, contrasting beautifully with the tender, juicy peaches inside.
