Preheat oven to 350 degrees. Grease a 9x5 inch loaf pan well.
In a medium bowl, whisk together the flour, baking powder, and salt.
In a larger bowl, whisk together the granulated sugar, milk, vegetable oil, egg, and vanilla extract. Add the dry ingredients to the wet ingredients and stir just until combined. Fold in the fresh blueberries
Spoon the batter into a greased 9x5-inch loaf pan. In a small bowl, combine the brown sugar, flour, cinnamon, and butter. Sprinkle it over the bread and bake for about 55-60 minutes or until a toothpick inserted in the center comes out clean or with a few moist crumbs.
Let the bread cool in the pan for 10-15 minutes before inverting on to a wire rack.
Notes
Do not overmix the dough. Mix just until the ingredients are incorporated. Overmixing the dough can result in tough bread.
You can use frozen blueberries, but don't thaw them. This keeps them from bleeding so much.
Store the cooled loaf in an airtight container or zipper bag for up to 4 days at room temperature. For longer storage, freeze the loaf.