Combine the beef, beef stock, bouillon cubes, tomato sauce and tomatoes, celery and onion in a slow cooker.
Add the frozen vegetables and spices.
Cover and cook on low for 6-7 hours or on high for 3-4 hours.
Stir well before serving.
Top with fresh parsley, if desired.
*If I do not have leftover roast beef, I use lean beef stew meat, trimmed and cut into small 1" chunks. Then I just add it to the slow cooker with the rest of the ingredients and cook on low for 7-8 hours or until the beef is fork-tender.