Place turkey carcass in 8-qt. stockpot. Chop 1 onion; set aside. Cut remaining onion into quarters; add to stockpot with carrots, celery, bay leaves, garlic and water. Bring to boil. Simmer on low heat 2 hours, skimming surface as needed and cooking the bacon in skillet until crisp after 1-3/4 hours. Transfer bacon to paper towels; drain, reserving drippings in skillet. Add chopped onions to drippings in skillet; cook and stir 5 min. or until crisp-tender.
Strain turkey broth; discard strained solids. Return broth to pot. Stir in bacon, chopped onions and all remaining ingredients except radishes and lettuce. Bring to boil; simmer on medium-low heat 15 min.