Place potatoes in a lightly greased 5-qt. slow cooker; sprinkle with salt and pepper. In a large skillet, cook beef and onion over medium heat until meat is no longer pink; drain. Spoon over potatoes. Top with vegetables.
Combine soup and milk; pour over vegetables. Cover and cook on low for 4 to 4-1/2 hours.
Top with cheese; cover and cook 30 minutes longer or until cheese is melted. Just before serving, sprinkle with french-fried onions.