Whisk together marinade ingredients and put in a shallow dish or zip top plastic bag. Marinate steak for a minimum of 1 hour but I highly recommend 3-4 hours.
While steak is marinating, make chimichurri by chopping up all ingredients or adding to a food processor and pulsing a few times. If you use a food processor, leave it roughly pulsed, you want some texture to the sauce.
Remove steak from marinade and pat dry with paper towels.
Heat grill or grill pan to high and grill on each side for 5-7 minutes for medium rare.
Let steak rest for 5-10 minutes then slice thinly against the grain and top generously with chimichurri sauce.