In a mixing bowl, whisk together the lemon juice, olive oil, lemon zest, minced garlic, oregano, thyme, salt, and pepper to create the marinade.
Place the chicken breasts in a resealable plastic bag or shallow dish, then pour the marinade over the top, ensuring each piece is well-coated. Seal the bag or cover the dish, and refrigerate for at least 1 hour (or up to overnight for best flavor).
Preheat your grill to medium-high heat.
Remove the chicken from the marinade, discarding the leftover marinade.
Place the chicken breasts on the grill and cook for about 6-7 minutes on one side. Flip and grill for an additional 6-7 minutes, or until the internal temperature reaches 165°F (75°C).
Once cooked, remove the chicken from the grill and let it rest for 5 minutes before slicing.
Serve the grilled chicken garnished with fresh parsley and slices of lemon, if desired.