In a small bowl, combine the first 6 ingredients (oil through salt).
Place the flank steaks and rosemary in a large, zipper topped plastic bag and pour the marinade over it making sure the entire steak is covered.
Seal and place in refrigerator to marinate for at least 4 hours or overnight, turning the bag several times.
When ready to cook, remove steak from refrigerator and marinade. Season both sides with salt and pepper.
Heat the olive oil in a large skillet over high heat.
Add the steak and let it cook, undisturbed for 4 minutes. Using tongs, turn the steak and let cook another 4 minutes.
For medium rare, the meat thermometer should register 135° or be slightly firm to the touch. Let rest for 5 minutes before cutting into thin slices, being sure to cut against the grain.