Clean the grill grates, then rub them with oil using a paper towel or brush. This will prevent the vegetables from sticking to the grill.
Trim off the root ends of the bok choy, cut them in half lengthwise, and rinse. I like to thoroughly rinse them under a faucet to remove any dirt or debris.
Shake off extra water, pat them dry with a paper towel, and place them on a cookie sheet or large tray.
Preheat the grill to medium-high heat (375-400°F/190-205°C). Once preheated, you can lower the heat to medium if needed during cooking to prevent burning. You want to get the initial sear during the first 2 minutes.
Drizzle olive oil over the bok choy halves, making sure they are evenly coated. Season with salt and black pepper to taste.
Place the bok choy halves directly on the grill grates, cut side down.
Grill the bok choy for 2-3 minutes per side or until it starts to char and become tender. Use tongs or a grill spatula to carefully flip the bok choy halfway through the cooking time. Adjust cooking times until bok choy is tender. Don't walk away from the grill. Turn one knob off to reduce heat if desired.
Once the bok choy is cooked to your liking, carefully remove it from the grill using tongs or a spatula. Transfer to a serving platter.
Allow the grilled bok choy to cool for a few minutes.