Prepare the grill
Make the dressing while the grill is heating.
In a small bowl whisk together the vinegar, garlic, ginger, soy sauce, sherry, hoisin, mustard and olive oil. Set aside.
Brush the onion slices and yellow peppers with vegetable oil and season with salt and pepper.
Grill the vegetables slowly over medium heat until soft and slightly charred, about 10 minutes. take them off the grill and separate the onions slices into rings
Grill the steak to the desired doneness. About 6 minutes per side for medium. Cut the steak against the grain in 1/4 inch slices.
Toss the greens with a very light coating of dressing and arrange on a serving platter or plates. Spread the onions and peppers on top of the lettuce and arrange the sliced steak attractively on top. allowing the onions and peppers to show through.
Drizzle a little more dressing over the salad and serve warm.