1. Whisk together the olive oil, lemon juice, and honey. Add 1/2 teaspoon salt and 1/8 teaspoon pepper; set aside.
2. Heat a grill pan to high. Lightly coat chicken with olive oil spray, and season with remaining salt and pepper; cook over high heat 2 minutes per side or until just cooked through. Transfer to a cutting board; let stand 5 minutes.
3. In a serving bowl, toss tomatoes, cucumber, onion, feta, olives, and half the mint with vinaigrette. Slice chicken into 1/2-inch strips, add to salad, and toss gently. Place 1 cup romaine on each of 4 plates, top with chicken mixture and remaining mint.