Lightly brush the patties on both sides with oil, place on the griddle, and cook over direct medium heat, with the lid closed, until golden and firm, about 8 minutes, carefully turning once after 5 minutes. During the last 30 seconds to 1 minute of grilling time, toast the buns on the cooking grates, cut side down, over direct heat. Build each burger on a bun with sauce, lettuce, a patty, onion, and pepperoncini, if using. Serve warm.
Lightly brush the patties on both sides with oil, place on the griddle, and cook over medium heat, with the lid closed, until golden and firm, about 8 minutes, carefully turning once after 5 minutes. During the last 30 seconds to 1 minute of grilling time, toast the buns on the cooking grates, cut side down, over direct heat. Build each burger on a bun with sauce, lettuce, a patty, onion, and pepperoncini, if using. Serve warm.