In a bowl, combine olive oil, red wine vinegar, minced garlic, finely chopped onion, dried Greek oregano, chopped fresh parsley, chopped fresh mint, and freshly cracked black pepper.

Mix all the ingredients well to create the marinade.

Add the cubed lamb shoulder or pork loin to the marinade, tossing to ensure the meat is fully coated.

Cover the bowl and refrigerate. Marinate for a minimum of 2 hours, but preferably overnight for the best flavor.

If using wooden skewers, soak them in water overnight or for at least 2 hours to prevent burning during grilling.

Preheat the grill to medium-high heat.

Thread the marinated meat evenly onto 4 skewers.

Season the skewers with coarse salt and freshly cracked black pepper.

Place the skewers on the preheated grill and cook for 4 to 5 minutes per side for medium doneness.

For well-done souvlaki, cook for 6 to 7 minutes per side.

Remove the grilled souvlaki from the grill and let rest briefly.

Serve the Greek Souvlaki hot with tzatziki sauce and warm pita bread.