Preheat oven to 350°F. Toss garlic with oil in baking pan. Cover with foil and bake for 30 minutes. Uncover and bake until garlic is tender, about 15 minutes. Allow garlic to cool. Peel and chop.
Cook potatoes in large pot of boiling salted water until tender, about 25 minutes. Drain. Transfer potatoes to large bowl. Add garlic and remaining ingredients. Using electric mixer, beat mixture until smooth. Season to taste with salt and pepper