In a shallow dish, combine all ingredients except the steak.
Place the flank steak in the marinated, turning to coat well on all sides. Cover and refrigerate overnight. Turn the steak every few hours.
When the flank steak is ready to cook, heat a grill to very high heat, around 450 degrees. Shake the excess marinade from the steak and place the steak directly on the grill.
Cook for 4 minutes, rotate 45 degrees, and cook for another 3 minutes. Flip and repeat, cooking for 4 minutes, rotating and another 3 minutes.
Remove the flank steak from the grill and cover with foil. Let rest for 15 minutes.
Transfer the grilled marinated flank steak to a cutting board. Using a serrated knife, slice the flank steaks in thin strips across the grain. Serve warm with roasted vegetables and chimichurri sauce.
For the Chimichurri Sauce
Combine all ingredients well in a bowl or jar.
Let rest at room temperature for at least 30 minutes. Serve with your favorite grilled meats and vegetables.
Notes
If you do not have time to marinate overnight, at least marinate for 3 hours. (Or use a vacuum sealer system for quick marinating.)Cooking times of your flank steak will vary based on thickness of steak, grill temperature, grill type and preferred doneness. To control the heat level of your chimichurri sauce, you can leave out the chiles.