Preheat oven to 350˚F and either grease a 9x9" baking pan or line it with parchment paper. Gather all your ingredients.
In a medium bowl mix the flour, rolled oats and brown sugar. Pour the melted butter and combine until fully incorporated. Remove 1 cup of this mixture and set aside for topping.
In a separate bowl, dice apples and sprinkle with granulated sugar, cinnamon and nutmeg. Set aside.
Add the apple sauce to the oatmeal mixture and stir. Pour into prepared pan and spread evenly.
Spread the diced apple layer over the base. Then sprinkle the reserved 1 cup of topping evenly over the apple layer.
Bake for 40-45 minutes or until lightly browned. Cool on a cooling rack.
Notes
Calorie count is an estimate and will vary based on ingredients and cooking methods used.