Toss potatoes, onions, red pepper and olive oil in large bowl. Sprinkle with Wish-Bone® House Italian Dressing & Seasoning Mix; toss to coat.
Evenly spread mixture down center of 12 x 18-inch piece heavy-duty aluminum foil. Wrap foil loosely around vegetable mixture, sealing edges airtight with double fold. Grill, turning twice, until potatoes are tender, about 30 minutes. Sprinkle with parsley.