01 - Preheat the oven to 350°F. Grease a 2-quart baking dish lightly with butter or cooking spray.
02 - In a large bowl, combine the peach slices, granulated sugar, flour, cinnamon, nutmeg, lemon juice, and salt. Toss thoroughly until the peaches are evenly coated with the spice mixture. Pour the mixture into the prepared baking dish and spread evenly.
03 - In a separate bowl, whisk together the flour, oats, brown sugar, cinnamon, and salt. Add the cold, cubed butter. Using your fingers or a pastry cutter, work the butter into the dry ingredients until the mixture forms coarse, pea-sized crumbs.
04 - Sprinkle the crumble mixture evenly over the peach filling, covering the fruit completely.
05 - Bake for 35 minutes, or until the topping is golden brown and the fruit filling is bubbling around the edges.
06 - Let the crumble cool for at least 10 minutes before serving. Serve warm with vanilla ice cream or whipped cream if desired.