Streusel-Topped Blueberry Muffins

3/4 c. milk
1/4 c. oil
1 egg
2 c. flour
1/2 c. sugar
2 tsp. baking powder
1/2 tsp. salt
1 c. blueberries (I always use frozen, but canned works too)  
Topping: 1/4 c. flour 1/4 c. brown sugar 1/4 tsp. cinnamon 2 T. butter

Heat oven to 400 degrees. Line muffin tin with papers. In a large bowl, beat milk, oil, and egg until blended. Add flour sugar, baking powder, and salt all at once stir just until four is moistened. Batter will be lumpy. Gently stir in blueberries. Divide batter among muffin cups and top with 1 T. streusel each.
For streusel topping: Mix flour, sugar and cinnamon, then cut in butter until mixture resembles fine crumbs. Bake muffins 20-25 minutes or until golden brown. Immediately remove from pan to wire rack.