In a medium-sized mixing bowl, whisk together lemon juice, olive oil, minced garlic, Dijon mustard, and dried oregano until emulsified and smooth.

Place chicken pieces in a sealable bag or shallow glass dish and pour marinade over, ensuring every piece is coated. Massage the marinade into the chicken.

Seal the bag or cover the dish with plastic wrap and refrigerate for 4 to 8 hours.

Preheat grill or oven to medium-high heat. Remove chicken from marinade and cook until the internal temperature reaches 165°F.

Once cooked, let the chicken rest for 5 minutes before serving with a Greek salad or pita.