Cut 1 orange into slices; cut remaining orange into wedges. With fingers, carefully loosen the skin from both sides of chicken breast. Place orange slices under the skin. Place orange wedges inside cavity and sprinkle chicken with 1/4 teaspoon pepper.
Tuck wings under chicken. Place breast side up on a rack in a shallow roasting pan. Combine the butter, garlic, basil, salt, onion powder, marjoram and remaining pepper; rub over chicken.
Bake, uncovered, at 350° for 30 minutes. Meanwhile, in a large bowl, combine the champagne, onions, broth and orange juice; pour into pan. Bake until a thermometer reads 175°, 1-1/2 to 2 hours longer, basting occasionally with pan juices. Cover loosely with foil if chicken browns too quickly. Cover and let stand for 15 minutes before slicing.
For gravy, pour drippings and loosened browned bits into a measuring cup. Skim fat, reserving 1 tablespoon. Add enough broth to the drippings to measure 1 cup. In a small saucepan, melt butter and reserved fat. Stir in flour until smooth, gradually add broth mixture. Bring to a boil; cook and stir until thickened, about 2 minutes. Serve with chicken.