In a large mixing bowl, combine the shredded chicken, crumbled bacon, ranch dressing, green onions, and shredded cheddar cheese.
Mix until the chicken is thoroughly coated and the ingredients are evenly distributed.
Season the mixture with black pepper and stir briefly.
Thoroughly wash and pat dry the butter lettuce leaves to ensure they remain crisp.
Place approximately 3 tablespoons of the chicken mixture into the center of each lettuce leaf.
Garnish with diced tomatoes and serve immediately.