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 on your cutting board, and cut the onions into ½ inch thick slices. Cut off the root and discard. You should get about 4-6 rings per onion. Carefully slide the metal skewers through the center of the onion rings, while holding down the rings with your other hand.
For grilled onion chunks:
Cut the onion in half vertically. Make three vertical cuts into each half and then slice them in half crosswise. Cut off the root and discard. You should get 12 chunks per onion. Carefully slide the metal skewers from the smaller part of the onion chunk through to the larger side. Add as many onion chunks that can fit on a skewer (3-6)
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 on both 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 off the grill and have softened.
Serve immediately with fresh parsley, if desired.
Notes
Tip: When grilling onion slices or chunks don't leave out the skewer. It really makes a difference and will keep more onions on your plate than down in the grate!