In a large mixing bowl, mash the ripe bananas until smooth. The riper they are, the better
Add the peanut butter, honey (or maple syrup), vanilla extract, milk, and egg to the mashed bananas. Whisk everything together until smooth and creamy
In a separate bowl, mix the rolled oats, baking powder, cinnamon, and salt. Then pour the dry mixture into the wet ingredients and stir until fully combined.
Preheat your oven to 375°F (190°C) and lightly grease an 8×8-inch baking dish with butter or non-stick spray. Pour the oatmeal mixture into the dish, spreading it evenly with a spatula.
Bake for 30–35 minutes, or until the top is golden and the center is set.
Once baked, let the oatmeal cool for about 10 minutes before slicing.