Cut beef into 6 serving-size pieces; sprinkle with seasoned salt and pepper. Layer beef and onion in 3- to 4-quart slow cooker. Pour pasta sauce over top.
Cover and cook on Low heat setting 8 to 9 hours.
About 20 minutes before serving, stir in tortellini and zucchini. Increase heat setting to High. Cover and cook 15 to 20 minutes or until tortellini are tender.