Mix all marinade ingredients in a large zip bag. Smash the ingredients around to mix them together. Add the steak and marinate for 3 to 12 hours (zipped up tight and kept in refrigerated).
15 minutes before grilling, remove the steak from the refrigerator and let it sit at room temperature. Preheat your grill to medium. Remove the steak from the marinade and grill 5 to 8 minutes per side (depending on how well-done you like your steak). Remove from the grill and let rest on a cutting board for at least 5 minutes before slicing. Slice against the grain. Serve and eat!
Notes
NOTE: nutritional information was calculated based on the assumption that you will be consuming ALL of the marinade. It's most likely that you will discard much of the marinade after marinating the steak. So the numbers are probably less than reported here.
*You can substitute flank steak for the skirt steak with similar results. You may need to increase grilling times a little bit as flank is usually thicker than skirt.