HEAT oven to 350°F.
COOK potatoes in boiling water 15 min. or just until tender; drain. Cut thin slice off of top of each potato. Scoop out centers into bowl, leaving ¼-inch-thick shells.
ADD sour cream, onions, bacon and potato tops to potatoes in bowl; mash until blended. Spoon into potato shells; sprinkle with cheese. Place in shallow baking dish.
BAKE 10 min. or until heated through.