In a large crockpot, add the olive oil, diced onion, and minced garlic. Sauté for about 3-4 minutes until the onion is translucent.
Add the chicken breasts, chicken broth, carrots, celery, thyme, oregano, bay leaf, salt, and pepper to the crockpot. Stir to combine.
Cover and cook on low for 6-8 hours or on high for 3-4 hours, until the chicken is cooked through and tender.
Remove the chicken breasts from the crockpot and shred them using two forks. Return the shredded chicken to the soup.
If using egg noodles, add them to the crockpot and cook on high for an additional 20-30 minutes until the noodles are tender.
Taste and adjust seasoning if needed. Remove the bay leaf before serving.
Serve hot, garnished with fresh parsley if desired.