Whisk together olive oil, lemon juice, garlic, vinegar, oregano, salt, and pepper in a bowl.
Place chicken in a resealable bag or shallow dish and pour the marinade over it.
Seal or cover and refrigerate for at least 30 minutes (up to overnight for more flavor).
Grill, bake, or pan-fry the chicken until fully cooked and golden on the outside.
Serve warm with your favorite Greek sides or over salad.