Preheat your oven to 350°F (175°C).
Line a muffin tin with paper liners or grease it.
In a large bowl, mix the mashed bananas and sugar until smooth.
Add the eggs, milk, and vegetable oil, and whisk until well combined.
In another bowl, combine the rolled oats, flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture, stirring gently.
Incorporate the vanilla extract.
Spoon the batter into the prepared muffin tin, filling each cup about three-quarters full.
Bake for 20-25 minutes, or until a toothpick inserted comes out clean.
Allow muffins to cool in the tin for 5 minutes before transferring to a wire rack.