Place ingredients for marinade in a blender or food processor then purée until relatively smooth. Pour marinade into resealable gallon-sized bag and set aside.
Trim skirt steak of excess fat and connective tissue. Place into bag with marinade, seal and refrigerate at least 8 hours and up to a full day.
Preheat grill to medium-high then remove steak from marinade, allowing a bit of marinade to cling to the meat. Blot the steak with paper towels to remove the liquid from the surface, but leave the veggie bits from the marinade clinging to the meat.
Oil grates well then add skirt steak. Grill 3–5 minutes per side or to desired degree of doneness. It is best served rare to medium-rare.
Remove from grill and allow meat to rest 5 minutes before slicing. Carve the meat against the grain into thin slices for most tender results.
One Last Thing
If you are unsure about how to choose a cut of meat, just ask the butcher!