Preheat a grill for medium heat (350° to 450°). Cook rice according to package directions.
Grill steak, turning once, until done the way you like, 8 minutes for medium-rare. Remove from grill, tent loosely with foil, and let rest 10 minutes before slicing thinly.
Meanwhile, in a small bowl, combine soy sauce, chile flakes, pepper, garlic, and oil.
Spoon about 1/4 cup rice onto middle of each lettuce leaf. Top with a little steak, a scant tsp. sauce, and onion strips.
Note: Nutritional analysis is per serving.