1. Preheat grill to 350° to 400° (medium-high) heat. Toss potatoes with olive oil; sprinkle with salt and pepper. Place, cut sides down, on cooking grate; grill, covered with grill lid, 2 minutes or until grill marks appear.
2. Remove from grill. Place potatoes in a single layer in center of a large piece of heavy-duty aluminum foil. Bring up foil sides over potatoes; double fold top and side edges to seal, making a packet. Grill potatoes, in foil packet, covered with grill lid, 15 minutes on each side.
3. Remove packet from grill. Carefully open packet, using tongs. Cool 5 minutes. Toss together potatoes, vinaigrette, next 4 ingredients, and, if desired, bacon.