Place 1 1/2 cups cereal in resealable food-storage plastic bag; seal bag. Using rolling pin, slightly crush cereal; set aside. In medium bowl, place muffin mix, milk and oil. Stir in egg just until moistened (batter will be lumpy). Stir in crushed cereal. Divide batter evenly among muffin cups. Sprinkle streusel evenly over tops.