Prepare the marinade by combining olive oil, soy sauce, balsamic vinegar, minced garlic, and rosemary.
Season the flank steak with salt and pepper on both sides.
Place the steak in a resealable bag and pour the marinade over it.
Seal the bag and refrigerate for at least 2 hours, preferably overnight.
Preheat your grill to medium-high heat.
Remove the steak from the marinade and discard the marinade.
Grill the steak for about 5-7 minutes on each side for medium rare.
Use a meat thermometer to check for doneness (130°F for medium rare).
Remove from the grill and let it rest for 10 minutes before slicing.
Slice against the grain and serve garnished with fresh herbs.