Preheat the oven to 375° F. Grease or line an 8x8 baking sheet with parchment paper and set aside.
In a bowl, whisk together the oats, baking powder, salt, and cinnamon. Set aside.
In a large bowl, whisk together the mashed bananas, milk, maple syrup, eggs, and vanilla until well combined. Pour in the oat mixture and mix until just combined. Add any additional add-ins at this time.
Pour this into the 8x8 pan and bake for 40-45 minutes, or until the center is set and top is golden brown. Allow it to cool for a few minutes before slicing and serving.
