Season chicken with salt and pepper on both sides.
Bake or grill chicken breasts to an internal temperature of 165°F. During last few minutes of cooking, baste the chicken breasts with 3/4 cups of the BBQ sauce, making sure to get both sides. Set aside to cool. Cut into bite-sized cube pieces. This, too, can be done in advance. Store, covered, in the refrigerator, until ready to use.
Starting at the top, with a very sharp knife, cut down into each avocado until you hit the pit. Cut completely around the avocado, top to bottom, touching the pit the entire time.
Pull the two halves of the avocado apart and remove the pit with a spoon.
Use the spoon to scoop the avocado out of the skin.
Cut avocado flesh into cubes.
Divide lettuce evenly among four large salad plates or bowls.
Add 1/4 of tomato, corn, black beans and avocado
Top each salad with 1/4 of the cubed up chicken breast.
Add a handful of the onion straws.
Top with a drizzle of the BBQ Ranch Dressing and a drizzle of the remaining BBQ sauce.
Sprinkle a bit of cilantro over top, to garnish.
Serve cold.