In a Dutch oven, heat oil over medium heat. Add onion and cook until tender, about 10 minutes, stirring frequently.
Add celery and cook for about five more minutes and then add garlic, stirring until fragrant.
Add chicken broth, bay leaves, basil, lemon juice and Worcestershire. Bring to a simmer and cook for 30 minutes.
Add bell pepper, mushrooms and chicken. Cover and simmer for 30 minutes.