Chimichurri sauce is as common in Argentina as ketchup is in the United States. I've seen a few other posted recipes for chimichurri sauce, but none that have quite the same list of ingredients that are included in this recipe. Prep time includes marinating time.
In a glass bowl, combine the oil, vinegar, lime juice, oregano, parsley, garlic and crushed red pepper. Season with salt, pepper and cayenne.
Place beef in a zip-lock plastic bag and add 3/4 cup (200ml) chimichurri sauce. Remove excess air from bag, seal it, and turn bag several times to coat beef with the sauce. Marinate in refrigerator for 2 hours. Cover the remaining sauce and refrigerate.
About 30 minutes before grilling, remove the beef and reserved sauce from the refrigerator. Soak wood chips in cold water. Heat a covered charcoal or gas grill to medium hot. Just before cooking toss the wood chips into the hot coals, or add the wood chips to the gas grill according to manufacturer's instructions.
NOTE: If using a strip loin, leave a 1/2-inch (1.25cm) layer of fat around the roast. For individual steaks, cut the meat into 6-ounce (170g) portions, about 1 1/2 inches (3.75cm) thick. Sear in a hot pan for 2 minutes on each side, and then grill for 4 to 5 minutes on each side, or as desired.
Grill the beef, turning occasionally and basting with the marinade from the bag until the outside is well browned and inside is cooked to desired degree, about 10 to 20 minutes. (A thermometer should register 125F°/52°C for medium-rare, or 135F°/57°C for medium.) Discard remaining marinade from the bag.
Transfer beef to a cutting board and let rest 10 minutes. Slice and transfer to a warmed serving platter. Drizzle the slices with some of the reserved chimichurri sauce and serve while still hot.