Stir the soup, soy sauce, vinegar, garlic powder, black pepper and beef in a 3 1/2-quart slow cooker. Cover and cook on LOW for 7 to 8 hours* or until the beef is fork-tender. Stir in the broccoli. Increase the heat to HIGH. Cover and cook for 15 minutes or until the broccoli is tender-crisp. Serve the beef mixture with the rice.