Preheat the oven to 350°F (175°C).
In a large bowl, combine the sliced apples, cranberries, granulated sugar, ground cinnamon, and ground nutmeg. Toss to coat the fruit evenly.
Pour the fruit mixture into a greased 9x9-inch baking dish.
In a separate bowl, combine the rolled oats, all-purpose flour, brown sugar, and chilled cubed butter. Use your fingers or a pastry cutter to mix the ingredients until they resemble coarse crumbs.
Sprinkle the oat crumble evenly over the fruit mixture in the baking dish.
Bake for 35-40 minutes, or until the topping is golden brown and the fruit is tender.
Remove from the oven and let cool slightly before serving. Serve warm with vanilla ice cream, if desired.
Enjoy!