If desired, heat olive oil in a skillet over medium heat. Add onions and garlic, sautéing for about 3-4 minutes until fragrant. This step enhances the flavor but can be skipped to save time.
Place the chicken breasts in the crockpot. Pour in the chicken broth.
Add sliced carrots, celery, chopped broccoli, sautéed onions, and minced garlic to the crockpot.
Sprinkle the thyme, oregano, salt, and black pepper over the ingredients. Add the bay leaf for extra flavor. Stir gently to mix.
Cover and cook on low for 6 hours or on high for 3 hours until the chicken is cooked through and vegetables are tender.
Once cooked, remove the chicken, shred it using two forks, and return it to the stew. Discard the bay leaf.
Stir well and serve hot. Adjust seasoning as needed.