Cut meat into 20 (3/4-inch) cubes. Sprinkle Worcestershire sauce over meat. Thread meat, bell pepper, tomatoes, mushrooms, and squash alternately onto 5 (12-inch) skewers. Sprinkle evenly with black pepper.
Place kebabs on grill rack coated with cooking spray; grill, uncovered, 10 minutes or to desired degree of doneness, turning once. Sprinkle evenly with salt.
Tip: If using wooden skewers, be sure to soak them in water 30 minutes before threading to keep them from burning during grilling.