Remove the skin from the chicken and trim off any visible fat.
Heat a large frypan with the oil over medium heat and brown the chicken on both sides. Place the chicken in the slow cooker.
Add the onions, peppers, and celery to the slow cooker.
Pour the wine into the frypan and stir and scrape up any browned bits from the chicken. Add the oregano and garlic paste and cook reducing the wine by half. Pour over the chicken mixture in the slow cooker. Add the tomatoes, parsley, salt, and pepper.
Set crockpot on low and cook for 7 hours.
When done turn the crock to high, remove the lid, and let bubble for one hour thicken.
Add the olives and let bubble for a few minutes to heat through.