How to Make It
Whisk mayonnaise, vinegar, salt, and pepper in a small bowl. Toss lettuce with half the dressing in a large bowl.
Place lettuce on a platter and top with tomatoes, tortilla chips, cucumber, and onion.
Toss chicken with barbecue sauce in a separate bowl; add to platter. Top salad with avocado. Serve remaining dressing on the side.