Preheat oven to 400°F (204°C). Line a muffin pan with paper liners and lightly grease the top.
In a large bowl, whisk flour, sugar, baking powder, and salt.
In a measuring jug, combine oil and egg. Add milk to reach 1 cup total, then mix in vanilla.
Pour wet ingredients into dry ingredients and gently stir until combined.
Fold in blueberries carefully without overmixing.
Divide batter evenly into muffin cups, filling nearly to the top.
Sprinkle sugar on top of each muffin.
Bake Easy Blueberry Muffins for 15–20 minutes until golden and set.
Cool on a rack before serving.