In a large bowl, combine ground beef, ranch dressing mix, egg, seasoned bread crumbs, and onion (Do not over-mix). Form mix into 4 patties.

Lightly oil the grill grate. Preheat the grill to medium-high heat.

Place patties on the grill, cook until the patties are golden brown and slightly charred (about 4-5 minutes per side) or until an internal temperature of 165 degrees is reached.

Top with cheddar cheese if desired. Serve on toasted buns with lettuce, tomato, onion, and ranch dressing.