- Preheat your oven to 350°F (175°C). Grease or line a muffin tin with liners. 
- In a mixing bowl, mash the ripe bananas with a fork until smooth. 
- Add the rolled oats, milk, honey or maple syrup, egg, and vanilla extract to the bowl with the mashed bananas. Stir well to combine. 
- In a separate small bowl, whisk together the baking powder, baking soda, cinnamon (if using), and salt. 
- Add the dry ingredients to the wet ingredients in the mixing bowl. Stir until just combined. Do not overmix. 
- Divide the batter evenly among the prepared muffin cups, filling each about 3/4 full. 
- Bake in the preheated oven for 18-22 minutes, or until the muffins are golden brown and a toothpick inserted into the center comes out clean. 
- Remove the muffin tin from the oven and let the muffins cool in the tin for a few minutes before transferring them to a wire rack to cool completely. 
- Serve the banana oat muffins warm or at room temperature. Enjoy!