In a small bowl, combine milk and rolled oats. Set aside for about 20 minutes so the oats soak up some of the milk.
Preheat oven to 425°F. Spray a 12-count muffin tin with cooking spray.
Whisk the dry ingredients in a large bowl; flour, baking powder, baking soda, cinnamon, and salt. Set aside.
Whisk the melted butter, honey, egg, and vanilla in a medium bowl until well combined.
Pour the wet ingredients in the dry ingredients, stir a few times, then add the oats (all the milk included) and the blueberries. Fold until just combined.
Spoon the batter into liners, filling them to the top.
Bake for 5 minutes at 425°F then reduce the temperature to 350°F. Bake for an additional 15-17 minutes or until a toothpick inserted in the center comes out clean.
Remove from the oven and allow the muffins to cool in the pan for 5 minutes before transferring to a wire rack to cool completely.
Notes
Muffins will keep in an airtight container at room temperature for a few days. They can be kept in the refrigerator for an additional week.