Combine oil, lemon juice and spices. Add steak and coat all over. Set aside covered to marinate for an hour, or overnight.
For the Chimichurri, place parsley, coriander, chilli, vinegar, cumin and garlic in a food processor, or finely chop herbs and garlic. Process ingredients, or mix well and add oil in a stream until incorporated. Season to taste. Refrigerate until required.
Pre-heat a barbecue grill or a grill plate over high heat and cook steak, searing well for 6-8 minutes each side, depending on thickness. Set aside covered for 5 minutes before slicing. Arrange on a board or serving plate and drizzle with chimichurri sauce. Accompany with crusty rolls.