Spray nonstick Dutch oven or large skillet with nonstick cooking spray. Heat over medium-high heat until hot. Add chicken; cook and stir 3 minutes or until no longer pink.
Add onions and celery; cover and cook 3 minutes or until celery is tender.
Stir in broth, soup, water, thyme and pepper until well mixed. Stir in frozen vegetables and barley. Bring to a boil. Reduce heat; cover and simmer 12 to 18 minutes or until barley is tender.