01 -
Lightly grease an 8x12-inch, 9x13-inch, or 9x9-inch baking pan with nonstick cooking spray, and set it aside. Preheat the oven to 325°F (if not refrigerating overnight).
02 -
In a large bowl, whisk together the oats, baking powder, cinnamon, nutmeg, salt, and brown sugar.
03 -
In a separate bowl or liquid measuring cup, whisk together the milk, eggs, and vanilla extract.
04 -
Pour the wet mixture over the dry ingredients and add the melted butter or coconut oil. Stir until combined.
05 -
Arrange the diced apples evenly over the bottom of the prepared baking dish. Pour the oatmeal mixture over the top.
06 -
You can cover and refrigerate the dish overnight or bake immediately. If refrigerated, uncover before baking.
07 -
Bake in the preheated oven for 35-45 minutes until the top is golden, and the mixture is set (not overly jiggly).
08 -
Serve warm or at room temperature. Optionally, pour a little milk over the top before serving.