This is great with fresh blueberries but doesn't work well with frozen.
1 1/2 cups all-purpose flour
3/4 cup white sugar
1/2 teaspoon salt
2 teaspoons baking powder
1/3 cup vegetable oil
1/2 cup buttermilk
1 teaspoon vanilla
1 cup fresh blueberries
1/2 cup brown sugar
1/3 cup all-purpose flour
1/4 cup butter, cubed
1 1/2 teaspoons ground cinnamon
Preheat oven to 400 degrees F. Grease muffin cups generously with spray, including tops or line with muffin liners.
Combine 1 1/2 cups flour, 3/4 cup sugar, salt and baking powder. Add vegetable oil, the egg, buttermilk and vanilla. Mix this with flour mixture. Fold in blueberries. Fill muffin cups about 2/3 full, and sprinkle with crumb topping mixture.
To Make Crumb Topping: Mix together 1/2 cup brown sugar, 1/3 cup flour, 1/4 cup butter, and 1 1/2 teaspoons cinnamon. Mix with fork, and sprinkle over muffins before baking.
Bake for 18 to 22 minutes in the preheated oven, or until done.