Grilled Flat Iron Steak with Blue Cheese-Chive Butter

Step 1
Whisk olive oil, vinegar, garlic, 1 tablespoon black pepper, rosemary, oregano, and kosher salt together in a bowl and pour into a resealable plastic bag. Add steak, coat with the marinade, squeeze out excess air, and seal the bag. Marinate in the refrigerator for 30 minutes.

Step 2
Preheat an outdoor grill for medium-high heat and lightly oil grate. Remove steak from the marinade, shake off excess, and discard remaining marinade. Allow steak to stand at room temperature as the grill warms.

Step 3
Meanwhile, mash butter, blue cheese, chives, and 1/8 teaspoon of black pepper together until combined; set aside.

Step 4
Cook steaks on the preheated grill until firm and reddish-pink and juicy in the center, about 5 minutes per side. An instant-read thermometer inserted into the center should read 130 degrees F (54 degrees C). Allow steak to rest in a warm place for 10 minutes before slicing thinly across the grain. Serve with a dollop of blue cheese-chive butter.