Cook bacon until crisp. Drain on paper towels. Crumble bacon; set aside.
Place potatoes in medium saucepan; add enough water to cover. Bring to a boil. Reduce heat to medium low; cover loosely and boil gently for 15 to 20 minutes or until potatoes break apart easily when pierced with fork. Drain well.
Mash potatoes until no lumps remain. Add salt,pepper and milk; continue mashing until potatoes are smooth. Spoon potatoes into medium bowl. Top with green onions,cheese and crumbled bacon.