Prep and cook chicken. Heat 2 tablespoons olive oil in a 12-inch skillet on medium-high heat. Use 1 ½ tablespoons barbecue seasoning to rub into the chicken breasts. Carefully place the chicken into the preheated skillet and cook for 3-5 minutes on each side until the chicken is fully cooked at 165 degrees Fahrenheit. Remove chicken from heat and transfer to a large plate.
Make dressing. While the chicken rests, place all of the cilantro ranch ingredients in a blender and blend for 15-20 seconds until the ingredients are completely incorporated. Add milk, a tablespoon at a time to reach the desired consistency if too thick. Place dressing in the fridge until ready to serve.
Chop and add sauce to chicken. Chop chicken and place in a medium-sized bowl. Stir in the remaining 1 ½ teaspoons of barbecue seasoning. Pour in ¼ cup barbecue sauce and stir until the chicken is completely coated in the sauce.
Assemble. To serve, place chopped lettuce in a large serving bowl. Top with chopped chicken, tomatoes, beans, corn, shredded cheese, avocado, onion, and tortilla strips. Sprinkle with green onions. You can line toppings up side by side in a wheel-like pattern or place ingredients on the lettuce and toss.
Add dressing and sauce. Drizzle with the desired amount of cilantro ranch dressing and barbecue sauce or serve sauces on the side for individual plating.