Preheat your oven to 350F and grease a 9x9" baking dish with cooking spray. Set aside.
In a large bowl, whisk together the milk, applesauce, maple syrup, oil, eggs and vanilla extract until smooth and combined
Then, add in the remaining ingredients (except for the apple) and stir with a spatula until combined.
Stir in about ⅔ of the diced apple. Then, pour the baked oatmeal batter into the prepared baking dish. Scatter the remaining apple chunks evenly over the top of the oatmeal.
Transfer baking dish to the oven to cook for about 45 minutes, or until mostly set. I like to let it cool pretty thoroughly before slicing so that it firms up. However, if you prefer more crumbly, moist baked oatmeal, feel free to cut into it earlier. Divide into 6 slices and enjoy!
