Place all vegetables in a plastic bag set into a shallow dish.
Pour Italian dressing over vegetables.
Marinate at room temperature 30 to 60 minutes, turning bag occasionally to distribute marinade.
Drain vegetables, reserving dressing.
On four 12-inch skewers alternately thread green pepper, red pepper, zucchini, and yellow squash, leaving space between pieces.
Place kabobs on the cooking grill.
Grill 10 to 12 minutes or till vegetables are tender, turning once halfway through grilling time and brushing occasionally with reserved dressing.