For streusel topping, mix 1/4 flour, 1/4 brown sugar, and 1/4 teaspoon cinnamon, then cut in 2 Tablespoons of cold butter or margarine. Set aside.
For muffins, mix 3/4 cup milk, 1/4 cup vegetable oil, 1 egg, 1/2 cup sugar, 1/2 teaspoon salt, 2 teaspoons baking powder, and 2 cups flour. If you wish, add 1 cup fresh or frozen blueberries.
Heat the oven to 400 degrees.
Spread some oil in the bottoms of muffin cups. Divide batter between 6 large or 12 regular size muffin cups.
Sprinkle the tops with streusel topping.
Bake 20-25 minutes or until toothpick pushed into the center comes out clean.