1. In a covered medium saucepan cook potatoes and onions in a small amount of lightly salted boiling water over medium heat for 8 to 10 minutes or until nearly tender, adding the squash and mushrooms for the last 1 minute of cooking time. Drain well. Cool slightly. If using wooden skewers, soak in water for 30 minutes before grilling.
2. On eight 10-inch skewers, alternately thread potatoes, onions, squash, mushrooms, and sweet peppers, leaving a 1/4-inch space between pieces. In a small bowl combine salad dressing, rosemary, salt, and pepper; brush over vegetables.
3. Place kabobs on the rack of an uncovered grill directly over medium coals. Grill for 10 to 12 minutes or until vegetables are tender and lightly browned, turning and brushing occasionally with dressing mixture. Makes 8 servings.
4. TO BROIL: Place kabobs on the greased unheated rack of a broiler pan. Broil about 3 to 4 inches from the heat for 10 to 12 minutes or until vegetables are tender and lightly browned, turning and brushing occasionally with dressing mixture.