Wash oranges; grate skins slightly.
Cover oranges with water Bring to a boil; simmer for 30 minutes.
Cut off small slice at blossom end; remove core.
Place 1 tablespoon sugar and 1 teaspoon butter in center of each orange.
Place in buttered baking dish; fill 2/3 full with water.
Bake, covered, in 350-degree oven for 2 hours.