Combine the garlic, jalapeno and vinegar in a bowl. Stir in the parsley, oregano, and lime juice. Whisk in the olive oil and season with salt and pepper. Mix well and set aside at room temperature to allow the flavors to marry.
Marinate the steak in olive oil for 30 minutes, turning to coat both sides.
Preheat an outdoor charcoal grill or oven broiler to high. Remove the steak from the oil and season both sides with a generous amount of salt and pepper; you should see the seasoning on the meat. Grill the steaks on the hottest part of the barbecue for 4 minutes per side, until well charred. Transfer the steak to a cutting board and let stand for 5 minutes. Cut the steak across the grain on the diagonal and fan the slices out on a platter. Spoon some chimichurri over the meat and serve with the remaining sauce at the table.