Preheat the oven to 350 degrees F. In a mixing bowl, toss the sliced apples with granulated sugar, cinnamon, nutmeg, and lemon juice until evenly coated.
Spread the apple mixture into an 8x8 inch baking dish and press it down lightly to create an even layer.
In a separate bowl, combine the rolled oats, flour, and brown sugar. Pour the melted butter over the dry ingredients and stir until the mixture forms clumps.
Sprinkle the oat topping evenly over the apples, covering them completely.
Bake for 35 to 40 minutes until the topping turns golden brown and the apples bubble around the edges.
Remove the dish from the oven and let it rest for 10 minutes. Scoop portions into bowls and top each serving with vanilla bean ice cream.