In a large skillet, cook the ground turkey and onion until the ground turkey is browned and the onions are soft.
In a large slow cooker, combine ground turkey, diced cabbage, tomato sauce, water, diced tomatoes, beef bouillon, Worcestershire sauce, minced garlic, brown sugar, celery salt, black pepper, salt, and dried parsley flakes.
Cook on high for 3-4 hours or low for 6-8 hours until the cabbage is tender. Add rice about 15-20 minutes before you're ready to serve so it heats through.