In a large bowl, whisk together olive oil, lemon juice, lemon zest, minced garlic, oregano, salt, black pepper, and red pepper flakes (if using) to create the marinade.
Add the chicken breasts to the marinade, ensuring they are well coated. Cover the bowl with plastic wrap and refrigerate for at least 30 minutes, ideally up to 2 hours for maximum flavor.
Preheat your grill or a grill pan over medium-high heat.
Remove the chicken from the marinade and let any excess drip off. Discard the remaining marinade.
Grill the chicken for 6-8 minutes on each side, or until the internal temperature reaches 165°F (75°C) and the chicken is golden brown.
Once cooked, transfer the chicken to a plate and let it rest for 5 minutes before slicing.
Garnish with fresh parsley before serving.
Notes
Serve with a fresh Greek salad for a complete meal.