Cut beef steak into 1-1/4 inch pieces. Combine marinade ingredients in a bowl, stirring well. Reserve 2 tablespoons marinade. Place half of remaining marinade and beef in food safe plastic bag; turn to coat. Place remaining marinade, squash and bell pepper in another food-safe plastic bag. Close bags securely; refrigerate 30 minutes to 2 hours, turning occasionally.
Remove beef and vegetables from marinade; discard marinade. Alternately thread beef and vegetables evenly onto four 15-inch metal skewers.
Place kabobs on grid over medium, ash-covered coals. Grill, covered, 8 to 10 minutes (over medium heat on preheated gas grill, 9 to 11 minutes) for medium rare (145º F) to medium (160º F) doneness, turning occasionally and brushing kabobs generously with reserved 2 tablespoons of marinade.