PREHEAT oven to 400° F. Line twelve medium muffin cups with paper baking cups or spray bottoms only with cooking spray.
COMBINE all ingredients in small bowl; mix well. Set aside.
COMBINE flour, oats, sugar, nuts, if desired, baking powder, pumpkin pie spice, baking soda and salt in large bowl; mix well. Combine pumpkin, milk, oil and egg in medium bowl; blend well. Add to dry ingredients all at once; stir just until dry ingredients are moistened. (Do not overmix.)
FILL muffin cups almost full. Sprinkle with reserved streusel, patting gently.
BAKE for 22 to 25 minutes or until golden brown. Cool in pan on wire rack for 5 minutes. Remove from pan. Serve warm.