Preheat oven to 350 degrees.
Prepare a 12 cup muffin pan with non-stick cooking spray or paper liners, and set aside.
In a large bowl, mix together the flour, sugar, baking powder, and salt.
In a separate medium bowl whisk together your milk, egg (the recipe card isn't saving the egg in my ingredients. This recipe calls for ONE EGG), oil and vanilla.
Pour the wet ingredients into the dry ingredients and mix gently just until combined.
Gently fold the blueberries into the batter.
Fill the muffin cups 3/4 with the muffin batter.
Bake in preheated oven for 15-20 minutes, until slightly golden brown on the top and a toothpick inserted in the center of the muffins comes out clean.
Slather with butter and enjoy!