In a large bowl, combine olive oil, lemon zest, lemon juice, garlic, salt and black pepper.
Trim chicken breasts of any excess fat and cut into thin strips. Place in bowl with marinade ingredients and set aside while preparing other recipe elements.
Preheat indoor or outdoor grill to high.
Slice 3 hearts of romaine in half lengthwise, brush with some olive oil, season with a little salt, and set aside.
Place hearts of romaine onto the grill and char quickly on each side. Remove from grill and set aside.
Reduce the heat of the grill. Slice the head of garlic in half to reveal cloves. Drizzle with olive oil, salt, and black pepper. Place onto the grill, cut side down to char and soften, about 7-10 minutes.
Remove garlic from grill when it has sufficient grill marks and has somewhat softened. Squeeze out 4 cloves and set aside for dressing.
Add the chicken to the grill and cook about 1-2 minutes per side or until internal temperature reaches 165° F. Remove chicken from the grill and cut into bite-size pieces.