Add the onion, carrots, chicken, celery, olive oil, vegeta or chicken broth, salt, pepper, water, bay leave and rosemary to your crockpot. Cook on low for 7 hours or 4 hours on high.
Remove the onion and take out the chicken to either cut into pieces or shred with two forks. Add chicken back to crockpot and add egg noodles. Cook for another 1 hour on high or until noodles are cooked.