Preheat your oven to 180°C.
Prepare your flax egg by mixing the ground flax and water in a small bowl and let sit for 2 minutes.
In a small (10 inch) casserole dish or baking pan add your oats, baking powder, salt, and cinnamon. Mix well.
To the casserole dish, add the flax egg mixture, oil, vanilla, and maple syrup, mixing well. Stir in your milk.
Add your optional extras such as: chopped apple, pecans, coconut flakes, and dried cranberries, mixing well.
Bake for 40 minutes. The baked oatmeal should be set, but moist.