In deep roasting pan combine the first 7 ingredients. Add roast and onions.
Seal and chill 3 to 24 hours. Turn meat occasionally.
To roast: remove seal. Roast covered with foil, at 325° for 1 1/2 hours, basting occasionally with marinade.
Halve any large potatoes. Add potatoes, carrots, and celery.
Continue roasting, covered for 1 to 1 1/4 hours; or until vegetables and roast are tender.
Remove meat; slice diagonally across the grain.
Return meat to pan; serve cooking juices with meat and vegetables.