In a large dutch oven or soup pot, heat oil over medium-high heat.
Add carrots, celery and onion and cook until onion is translucent, about 5 minutes, stirring often.
Add broth, chicken breasts (raw and whole), barley, salt and pepper.
Bring to a simmer, cover and reduce heat to medium-low. Cook, stirring occasionally, until barley is tender, about 45-60 minutes.
Remove chicken from pot and shred with two forks. Add back into soup, taste, and adjust salt and pepper to your preferences.