Preheat your oven to 350°F (175°C). Grease a muffin tin or line with muffin liners.
In a large mixing bowl, combine the rolled oats, baking powder, cinnamon, and salt.
In another bowl, whisk together the milk, mashed bananas, beaten eggs, and vanilla extract.
Pour the wet ingredients into the dry ingredients and mix until well combined.
Fold in the blueberries gently.
Spoon the mixture into the prepared muffin tin, filling each cup about ¾ full.
Bake for 25-30 minutes or until a toothpick inserted into the center comes out clean.
Allow to cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.