01 - In a medium bowl, whisk together the mayonnaise, lemon juice, olive oil, minced garlic, smoked paprika, oregano, salt, and pepper until smooth and well combined.
02 - Pat the chicken breasts dry with paper towels. Place them in a large resealable plastic bag or a shallow dish.
03 - Pour the marinade over the chicken, ensuring each piece is thoroughly coated. Seal the bag or cover the dish tightly, then refrigerate for 1 to 4 hours.
04 - Preheat your grill to medium-high heat, approximately 400°F. Clean and oil the grates to prevent sticking.
05 - Remove the chicken from the marinade, allowing any excess to drip off. Discard the remaining marinade. Grill the chicken for 6 to 8 minutes per side, or until the internal temperature reaches 165°F and juices run clear.
06 - Transfer the chicken to a cutting board and let it rest for 5 minutes. Slice against the grain, garnish with fresh parsley or chives if desired, and serve hot.