1Pour marinade over beef in resealable food-storage plastic bag or glass or plastic dish; coat beef with marinade. Let stand 15 minutes.
2Spray inside of 4- to 5-quart slow cooker with cooking spray. Place potatoes in slow cooker. Mix flour and Cajun seasoning; toss with beef and marinade, coating well. Place beef and marinade on potatoes. Add tomatoes.
3Cover; cook on Low heat setting 7 to 8 hours.
4Stir in stir-fry vegetables. Cover; cook on Low heat setting 15 to 30 minutes or until vegetables are tender.