Heat oil in a large skillet over high heat until the oil is very hot but not smoking.
Add in the steaks; cook until the undersides are well browned, about 3 minutes.
Decrease heat to medium; turn and cook until the other sides are browned and the steaks feel somewhat soft when pressed in the center, about 4 minutes more for medium-rare (do not cook skirt steak more than medium-rare, or it will toughen).
Transfer the steaks to 4 dinner plates.
Drain the fat from the skillet; add in the red wine, shallots, and garlic; bring to a boil over high heat.
Boil until the wine has reduced by half, about 3 minutes.
Decrease heat to very low; whisk in the butter, 1 tablespoon at a time, to slightly thicken the sauce.
Season with salt and pepper.
Pour some of the sauce over the steaks and sprinkle with parsley; serve immediately.