Preheat the oven to 375°F.
Spray an 8-inch square baking dish with cooking spray.
In a large bowl, mix together the oats, half the walnuts, baking powder, cinnamon, and salt.
Add in the milk, maple syrup, egg, coconut oil, vanilla and grated zucchini. Stir well to combine.
Carefully pour oatmeal mixture into the prepared baking dish.
Scatter the remaining walnuts across the top.
Bake for 40 minutes, until the top is nicely golden. Remove from the oven and let cool for a few minutes. Portion and serve. I like topping mine with peanut butter or almond butter and a splash of milk.
For storage: store in the refrigerator in an airtight container for up to 4 days.
To reheat: To reheat the whole baked oatmeal, cover with foil and reheat in a 350°F oven for about 20 minutes. For individual portions, set oven (or toaster oven) to 350°F and bake for 5-10 minutes or reheat in the microwave for 1 minute.