Spray an outdoor grill with non-stick spray and preheat to medium-high heat. Season both sides of the chicken with salt and pepper. Cook the chicken for about 4-6 minutes per side, or until the internal temperature is 165 degrees. Chicken is done if juices run clear when pierced with a fork. During last few minutes of cooking, baste the chicken breasts with BBQ sauce. Remove the chicken from the grill to a plate; cover and allow the chicken to rest for 3 minutes. Cut into bite sized cubes.
To assemble the salad, place romaine lettuce in a large bowl; top with chicken, tomatoes, corn, beans, onion, avocado and cheeses. Gently toss to combine. Serve immediately, drizzled with Ranch dressing and BBQ sauce. Garnish with chopped cilantro and tortilla strips if desired.