Have butcher bone leg of lamb and remove all visible outside fat.

Cut lamb into 2-inch cubes, removing all fat and gristle.

Ensure only lean solid meat is used for kebabs.

Place lamb meat and sliced onions in a large bowl.

Add red wine, extra virgin olive oil, fresh oregano, salt, and freshly ground black pepper to the bowl.

Mix well to ensure all lamb pieces are coated in the marinade.

Chill the mixture for at least 4 hours, preferably overnight, to allow the flavors to meld.

Before grilling, soak wooden skewers in cool water for 20 minutes to prevent burning.

Remove meat from the marinade.

Thread the marinated lamb cubes onto the soaked skewers.

Preheat grill to medium-high heat.

Grill the lamb skewers over medium-high heat, turning frequently to cook evenly.

Cook for about 15 minutes for medium-rare or 25 minutes for medium doneness.

Serve immediately.