Place potatoes in a Dutch oven; add water to cover. Bring to a boil. Reduce heat; cook, uncovered, 10-15 minutes or until tender., Meanwhile, in a skillet, cook bacon over medium heat until crisp. Remove to paper towels with a slotted spoon; drain., Drain potatoes; return to pan. Mash potatoes, gradually adding cream cheese, sour cream and butter. Stir in milk and seasonings. Transfer to a greased 13x9-in. baking dish; sprinkle with cheese, green onions and bacon. Refrigerate, covered, up to 1 day., Preheat oven to 350°. Remove potatoes from refrigerator and let stand while oven heats. Bake, covered, about 30 minutes. Uncover; bake 10 minutes longer or until heated through.