Peel off the outer layers of the onions and discard. Leave the root end intact to make it easier to cut the onions.
For grilled onion slices:
Lay the onion on its side and cut into ½-inch thick slices. Cut off the root and discard. You should get about 4–6 rings per onion. Slide the metal skewers through the center of the onion rings, holding them in place with your other hand.
For grilled onion chunks:
Cut the onion in half vertically, then cut each in half again to make small wedges. Cut off the root and discard. You should get 12 chunks per onion. Slide the metal skewers from the smaller part of the onion chunk through to the larger side.
Grilling Instructions:
Drizzle the onions with olive oil and season with salt and pepper. Use a brush to spread the olive oil and seasoning all over the onions, coating all sides.
Preheat the grill or grill pan to medium heat and oil the grates or pan. Place the onion skewers directly on the grill. Cook for 5 minutes, then try to flip (if sticky, keep on for 1–2 more minutes), and cook for 5–7 more minutes until they easily release from the grill and have softened.
Serve immediately with fresh parsley, if desired.
Notes
Storage: Store leftovers in the fridge for up to 4 days.