Place the chicken cubes in a large mixing bowl. Add olive oil, lemon juice, garlic, oregano, parsley, salt, and black pepper. Stir well to ensure the chicken is evenly coated. Refrigerate and marinate for a minimum of 30 minutes.
Preheat the grill to medium-high heat. Thread the marinated chicken pieces onto skewers, using 8 to 9 cubes per skewer to yield approximately 6 skewers.
Grill the skewers for 3 to 4 minutes per side, turning occasionally, until the chicken is fully cooked and lightly charred.
Serve immediately with tzatziki sauce for a refreshing and authentic accompaniment.