1. Thread onions onto metal skewers; place on baking sheet and brush each side with oil. Season each side generously with salt and pepper.

2. Light large chimney starter filled with charcoal (6 qts, or about 100 briquettes) and allow to burn until coals are fully ignited and partially covered with thin layer of ash, about 20 minutes. Empty coals into grill; build two-level fire by stacking two-thirds of coals in one half of grill and arranging remaining coals in single layer in other half. Position cooking grate over coals, cover grill, and heat until grate is hot, about 5 minutes; scrape grate clean with grill brush. Place onions over cooler side of grill and cover with aluminum pan.

3. Grill onions, covered, until onion rounds are deep golden brown and just tender, 15 to 20 minutes, checking onions every 5 minutes and flipping and rotating skewers as needed to ensure even cooking. Transfer onions to platter and remove skewers; discard any outer charred rings. Serve hot, warm, or at room temperature.

Serves 4