Cook bacon in a skillet or 400°F oven until crisp, 12–15 minutes. Drain on paper towels and cool.
Chop the chicken, tomatoes, romaine, celery, green onions, and parsley. Set aside.
Whisk mayonnaise, Greek yogurt, lemon juice, Dijon, garlic powder, salt, and pepper in a large bowl.
Fold in the chicken until coated with the dressing.
Stir in celery, green onions, and tomatoes. Mix gently to keep tomatoes intact.
Add the crumbled bacon and romaine just before serving. Toss lightly and sprinkle with parsley.
Chill 10–15 minutes for flavors to meld, if time allows. Serve as desired.