Preheat your oven to 350°F (175°C). Grease a muffin tin or line with muffin liners.
In a large bowl, mix the oats, flour, baking powder, baking soda, and salt.
In another bowl, combine the mashed bananas, egg, honey, milk, and vanilla extract.
Pour the wet ingredients into the dry ingredients and stir until just combined.
Divide the batter evenly among the muffin cups.
Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Let the muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.