In small bowl, beat milk, oil and egg until well blended. Add to flour mixture all at once; stir just until dry ingredients are moistened (batter will be lumpy). Stir in blueberries and lemon peel. Divide batter evenly among muffin cups. Struesel Topping: Mix flour, brown sugar and cinnamon; cut in butter with pastry blender. Spinkle each muffin with about 1-2 teaspoons streusel topping.