Bistro Cheeseburger

1 1/2 pounds ground beef
4 slices sweet onion (1/2-inch)
Vegetable oil
8 slices Swiss cheese
1/4 cup mayonnaise
1 tablespoon Dijon-style mustard
4 crusty rolls, split, toasted
Romaine lettuce, tomato slices

1. Lightly shape ground beef into four 3/4-inch thick patties. Brush onion with oil. Place patties in center of grid over medium, ash-covered coals; arrange onion around patties. Grill, uncovered, 13 to 15 minutes to medium (160°F) doneness, until patties are not pink in center and juices show no pink color and onions are tender, turning occasionally. Season with salt and pepper after turning. About 1 minute before patties are done, top each with 2 cheese slices.
2. Combine mayonnaise and mustard; spread on top halves of rolls. Serve burgers and onion in rolls with lettuce and tomato.

Makes 4 servings