On a hot grill, onions are a fast-moving beast. Slice them thick—half-inch rounds, at least—so they don’t fall through the grate. Grilled onions are done in 8 to 12 minutes, flipping once or twice, depending on your heat. You want those dark, charred stripes that scream "backyard barbecue."
Onion Frying Pan
But here’s the ironic part: if you slice them too thin, they dry out. They become crispy, burnt wisps that crumble into the ashes. Nobody wants that. So go thick, let them steam a little inside, and get the char on the outside. Serve them on a hot dog and pretend you’re at a ballpark.