First ingredient in the version published in EatingWell Magazine is 6 cups of chopped romaine or iceberg lettuce.
From EatingWell: July/August 2013
We gave a classic chef’s salad recipe a healthy makeover with our own homemade healthy Thousand Island dressing recipe and reduced-sodium cheese and turkey. Those swaps slashed 260 calories and nearly a day’s worth of sodium (2,131 mg!) per serving compared with traditional recipes.