Blend 1/2 cup low-calorie Italian salad dressing, 1/4 cup soy sauce, 1/4 cup finely chopped onion, and 1 teaspoon dry mustard; mix well.
Halve and skin three 1 3/4 pound ready to-cook broiler fryer chickens; brush with soy mixture.
Place chicken in bottom of broiler pan (no rack).
Broil 5 to 7 inches from heat for 20 minutes; brush occasionally.
Broil till meat is tender, about 20 minutes; brush occasionally with mixture.