Preheat grill to medium heat. On a work surface, arrange 2 rectangles of heavy-duty foil large enough to fit the potatoes side-by-side.
Place potatoes in the center of one of the rectangles, leaving enough room around the sides to close, and drizzle with olive oil and seasoning mix. Cover with the remaining rectangle of foil, pinch sides to form a packet, and shake 6 to 8 times to mix well.
Set packets on grill and cook until fork tender, 25 to 30 minutes. After 20 minutes, spray the grill with oil and cook the spring onions until tender, approximately 5 to 10 minutes.
Transfer potatoes to a serving platter, then slice the spring onions to serve alongside. Garnish with chives and serve dressing for dipping, if desired.
For safe meat preparation, reference the USDA website.