Preheat oven to 375°. In large bowl, combine sweet potatoes, brown sugar, 1/4 c melted butter or margarine, salt and nutmeg. Beat at medium speed on electric mixer until smooth and well blended. Section oranges. Fold 1/2 of the sections into potato mixture. Pile into a 2-quart casserole. In cup, combine pecans, brown sugar and 2 T melted butter or margarine. Sprinkle over top of potato mixture. Arrange remaining orange sections in circle over mixture. Cover casserole. Bake at 350° for 1 hour.