In a resealable zip-top bag, add chicken, salt, pepper, garlic powder and marinate for at least 30 minutes.
Preheat grill to medium-high heat and cook for 4-5 minutes on each side or until the internal temperature reaches 165 F. Remove the chicken from the grill and tent with foil. Let it rest and cool a bit for about 10 minutes and then slice or chop into bite-sized pieces.
Whisk together all the ingredients for the vinaigrette. Drizzle 1 teaspoon over the sliced avocado (to prevent from browning).
In a large bowl, add the lettuce, then top with avocados, bacon, tomatoes, cucumbers, berries, and cheese. Drizzle with dressing right before serving.