01 - In a large bowl, whisk together mayonnaise, lemon juice, garlic, Dijon mustard, smoked paprika, oregano, salt, and pepper until smooth and well combined.
02 - Add the chicken breasts to the marinade and turn to coat thoroughly on all sides. Cover and refrigerate for at least 2 hours, or overnight for best flavor.
03 - Preheat the grill to medium-high heat (about 400°F). Brush the grates with olive oil to prevent sticking.
04 - Remove chicken from the marinade, allowing excess to drip off. Grill chicken for 6 to 8 minutes per side, or until the internal temperature reaches 165°F and the juices run clear.
05 - Remove chicken from the grill and let rest for 5 minutes before slicing or serving.