Place the chopped garlic, oregano, basil, parsley, rosemary, and salt into a mortar or small bowl, and mash into a coarse paste.
Stir in the olive oil, balsamic vinegar, and pepper until evenly blended.
Set half of the mixture aside. Spread the remaining half of the herb mixture evenly over the steaks. Set aside to marinate for 1 hour.
Preheat an outdoor grill (or indoor grill pan) and lightly oil the grate.
Cook the steaks on the preheated grill for 7 minutes, then turn over and coat with the reserved herb mixture.
Continue cooking 7 minutes more, until the desired doneness.
Let rest 5-10 minutes prior to serving.