First, place all ingredients for the dressing/marinade in a glass jar with a lid and shake until combined.
Place the sliced chicken pieces into a Ziplock bag, add 1/3 a cup of the marinade, close the bag, and massage the bag until the chicken is fully coated. Place the bag in the refrigerator and allow it to marinade for at least 2 hours, up to 24.
Next, combine the black beans, sweet corn, bell peppers, onion, and 1/3 cup of the marinade/dressing in a bowl. Mix until everything is combined. Store in an airtight container for at least an hour so the flavors meld.
When you are ready to make the salad, remove the chicken from the Ziplock bag, discarding the marinade. Cook the sliced chicken in a skillet or cast-iron pan for about 5-7 minutes, stirring a couple of times, until the chicken is cooked throughout.
Arrange the lettuce on a large serving platter, top with the cowboy caviar mixture, cooked chicken, and avocado slices. Serve with the remaining dressing/marinade on the side.