Place marinade ingredients in a blender and blend until smooth. Add the marinade and steak to a large zip top bag and refrigerate for at least 1 hour to allow flavors to be imparted to the steak.
Heat a grill to medium high and grill the steak to desired doneness. Slice into strips for use in the tacos.
Chimichurri Sauce
Add all sauce ingredients to a blender and blend until almost smooth. Some small chunks are desirable and add good texture so there is no need to blend until completely smooth.
Taco Assembly and Toppings
Heat tortillas any way you desire or use them as is. I prefer to steam them in damp paper towels in the microwave or lightly fry them in olive oil if I want a slightly crisp tortilla.
Add steak strips to tortillas and then top with chimichurri sauce and any additional toppings you desire.