HOMESTYLE CHICKEN BARLEY SOUP

1 Tbs vegetable oil
1 cup onion, chopped
1 cup carrots, chopped
1 cup celery, sliced
4- 1/4 cups water
2 cups chicken stock
1/2 cup pearled barley
1/2 lb cooked chicken

Heat oil in a heavy saucepan or Dutch oven over medium heat. Sauté next 3 ingredients 4-5 minutes until onion is tender. Add remaining ingredients, except chicken. Increase heat to high and bring to a boil. Reduce heat to low and simmer 40 minutes, stirring occasionally. Add cooked chicken and continue to simmer 5-10 minutes or until chicken is heated through and barley is tender.