Heat vegetable oil in a large stockpot over medium heat. Add chicken breasts and sear until cooked through, about 5 minutes per side. Remove chicken from stockpot and set aside once cooked.
Add garlic to stockpot and saute until fragrant, about 30 seconds.
Add onion, carrots, and celery and saute until slightly softened, about 3-5 minutes.
Add barley, chicken broth, bay leaf, dried parsley, dried rosemary, dried thyme, and ground black pepper and bring to a boil. Cover, reduce heat to low, and simmer until barley is tender, about 30 minutes.
Shred chicken, return to stockpot, stir well and enjoy!
Notes
Pearled barley can often be found with the other grains in the grocery store -- sometimes it's available in the bulk aisle as well!
Mix it up by adding brown rice, farro, or another whole grain instead of barley. Just make sure you adjust the cook time as needed.
Save time by using pre-cooked rotisserie chicken. Just shred about 2 cups worth and stir in at the end to warm it back up.
Store leftovers in an air-tight container in the refrigerator for up to 3-5 days.