Preheat the grill to 375°F (medium-high).
Place the potatoes in a single layer in the center of a large sheet of heavy-duty aluminum foil. Drizzle with olive oil and sprinkle with salt and pepper. Bring the foil sides up over the potatoes, then double-fold the top and side edges to seal, forming one large packet.
Grill the potatoes in the foil packet, covered with the grill lid, for 15 minutes per side. Remove the packet from the grill. Carefully open the packet with tongs, then let the potatoes cool for 10 minutes.
Whisk together the mayonnaise and the next 4 ingredients in a large bowl. Add the potatoes and toss gently to coat. Stir in the onion, blue cheese, and bacon, then serve. Serves 6-8.
Enjoy with Iron Hub Rosé.