Wash and dry the apple. Remove the core and seeds and dice into ½-inch cubes. Set to the side.
Grease a 2 quart or 8-inch square pan with a bit of the coconut oil.
To the greased pan, add the remaining 1½ tablespoons melted coconut oil, 1¾ cups milk, 1 large egg, ⅓ cup maple syrup, 1 teaspoon baking powder, 2 teaspoons ground cinnamon, ½ teaspoon nutmeg, and ⅛ teaspoon kosher salt. Whisk to combine.
Add the diced apples, 2 cups rolled oats, and ½ cup chopped nuts to the milk mixture and stir to combine.
Preheat the oven to 350℉ (175℃) and let the oatmeal sit at room temperature while the oven preheats. This will give the oats time to soften and absorb the milk.
Bake for 25-30 minutes, until oats are tender, set, and lightly golden.
Serve warm or let chill and refrigerate to enjoy later throughout the week.
Video
Notes
Oats: Use old-fashioned or quick-cooking oats for the best texture. Do NOT use steel-cut oats. Be sure to use certified gluten-free oats for a gluten-free baked oatmeal recipe.Apples: Use any firm apple suitable to baking (Granny Smith, Golden Delicious, Braeburn, Honey Crisp, etc.) I prefer a sweet apple here, but a tart apple works if you like your oatmeal a bit less sweet.Dairy-Free: Use your favorite non-dairy milk and coconut oil. Oil/Butter Free: Use applesauce in place of coconut oil/melted butter and nonstick spray to grease pan. Egg-Free: Simply omit the egg, keeping in mind your oatmeal won't set up into a cake-like consistency, but will still be deliciousStorage: Store leftover baked oatmeal in an airtight container in the fridge for up to 5 days. To freeze, slice, wrap in parchment, and place in a freezer bag. Reheat slices in a microwave-safe bowl in 30-second intervals, adding milk to loosen if needed.