Combine garlic, mint, oil, salt, pepper and lemon jioce in a small bowl. Slide vegetables and chicken on 2 long or 4 short skewers, alternating between mushroom, onion, chicken and peppers. Arrange skewers in a glass dish and pour lemon juice mixture over them, turning to coat. Cover and refrigerate 30 minutes. Spray a grill rack with non-stick cooking spray, and preheat to medium heat. Grill kebabs, covered, 5 to 7 minutes each side or until a meat thermometer in chicken registers to 170F. Serves 2.