Pierce potatoes several times with a fork and place on a microwave-safe plate. Microwave on high for 15-20 minutes or until tender, rotating the potatoes once. Let stand until cool enough to handle.
2
Meanwhile, in a large resealable plastic bag, combine the summer squash, zucchini, peppers and onion. Pour salad dressing over vegetables. Seal bag and turn to coat; marinate for 20 minutes.
3
Cut each potato in half lengthwise. Scoop out pulp, leaving a thin shell (save pulp for another use). Brush inside of shells with oil and sprinkle with 1/4 teaspoon salt.
4
Coat grill rack with nonstick cooking spray. Place potato shells skin side up on grill rack. Grill, covered, over indirect medium heat for 10 minutes or until golden brown.
5
Drain vegetables, reserving marinade. Grill vegetables in a grill basket, uncovered, over medium heat for 10 minutes or until tender, basting with reserved marinade.
6
Sprinkle potato skins with cheese. Fill with grilled vegetables; sprinkle with remaining salt. Grill 5 minutes longer or until cheese is melted.