Preheat the oven to 375° F and grease spray an 8×8 inch square or 11x7 rectangular baking dish with a little butter or coconut oil.
In a large bowl, mix together the oats, baking powder, cinnamon, and salt.
In a medium sized bowl, whisk together the milk, maple syrup, banana, eggs and vanilla. Pour into the large bowl with the dry ingredients and stir to combine. Then add the melted butter and mix just until incorporated. (I do this so the melted butter or coconut oil doesn’t solidify in the wet ingredients)
Fold in the chocolate chips.
Pour the oatmeal mixture into the prepared baking dish.
Bake for 25 to 35 minutes, until the top is nicely golden and the middle is set. Remove from the oven and let cool for a few minutes. Portion and serve. Drizzle each portion with additional maple syrup or serve with a dollop of your favorite yogurt.
To store: store in the refrigerator in an airtight container.
To reheat: To reheat the whole baked oatmeal, cover with foil and reheat in a 325°F oven for about 20 minutes. For individual portions, set oven to 325°F and bake for 5-10 minutes.