What You'll Need:
6 cloves garlic, minced
1/4 cup extra virgin olive oil
1/4 cup balsamic vinegar
2 tablespoons chopped fresh rosemary, divided
3/4 teaspoon salt
1/2 teaspoon black pepper
1 1/2 pound flat iron steak
In a bowl whisk together garlic, extra virgin olive oil, balsamic, 1 tablespoon chopped rosemary, salt and pepper.
Place flat iron steak in a resealable plastic bag. Pour marinade over the top. Shake to coat steak in marinade. Leave out for 2 - 3 hours, flipping and kneading when you think about it. When you're ready to cook, preheat your grill to medium-high heat.
Place the steak on the grill and reserve the marinade. Cook steak 4 - 6 minutes per-side for medium rare.
Remove steak from grill and let rest for 10 minutes. The steak will continue to cook a bit while resting.
Meanwhile, pour marinade into a skillet over medium heat. Bring to a boil and remove from heat.
After steak has rested, slice it against the grain into 1/2 inch slices. Spoon sauce over the top and serve.