In a mixing bowl, whisk together lemon juice, lemon zest, minced garlic, olive oil, soy sauce, Dijon mustard, honey, smoked paprika, cayenne pepper (if using), thyme, salt, and black pepper.
Marinate the Chicken
Place the chicken leg quarters in a large resealable bag or shallow dish. Pour the marinade over the chicken, ensuring every piece is well-coated. Seal the bag or cover the dish, then refrigerate for at least 4 hours (overnight for best flavor).
Preheat the Grill
Heat your grill to medium-high heat (about 375–400°F). Oil the grates to prevent sticking.
Grill the Chicken
Remove the chicken from the marinade, letting excess drip off, and place it on the grill skin-side down. Discard the remaining marinade. Grill for 10–12 minutes on the first side until nicely charred. Flip the chicken and grill for another 15–18 minutes, or until the internal temperature reaches 165°F (check with a meat thermometer near the thickest part, avoiding the bone).
Rest and Serve
Transfer the chicken to a serving plate and let it rest for 5 minutes to retain its juices. Garnish with fresh parsley and serve with lemon wedges for an extra burst of citrus.