In a medium bowl, whisk together the olive oil, lemon juice, lemon zest, parsley, minced garlic, kosher salt, and black pepper.
Place the chicken thighs in a large resealable plastic bag or shallow dish, pour the marinade over them, and toss to coat evenly. Refrigerate for at least 30 minutes, or up to 4 hours.
Preheat the grill to medium-high heat (about 375°F to 400°F). Oil the grates lightly.
Remove the chicken from the marinade, letting excess liquid drip off. Discard the remaining liquid.
Grill the chicken for 6 to 7 minutes per side, or until the internal temperature reaches 165°F on an instant-read thermometer.
Transfer the chicken to a plate, tent loosely with foil, and let rest for 5 minutes before serving.