Rub it in, why don'tcha! A zesty marinade lends flavor and crust to this perfectly grilled Flat Iron Steak. Preparation is easy, but precise, so make sure you've got plenty of time to marinate and bring back up to room temperature before grilling. Serve your flat iron steak family-style with your choice of sides.
Peel the garlic cloves, then smash and roughly chop. Use the flat side of a chef’s knife to pulverize the garlic into a paste-like consistency. Alternatively, mash the garlic using a mortar and pestle.
Transfer garlic to a small bowl. Add the olive oil, dijon mustard, lemon juice, zest, salt, and pepper. Mix until well combined.
Rub the marinade evenly over all sides of the steak. Arrange on a plate, cover with plastic wrap, and marinate in the fridge 4-6 hours.
Remove the steak from the fridge 1 hour prior to cooking to bring to room temperature.
Heat a gas grill to high heat or prepare a charcoal grill for both direct heat and indirect heat.
Gas Grill: Place the steaks on the grill in an even layer. Sear the steaks 2 minutes with the lid OPEN, flip the steaks, then sear 2 minutes more over high heat. Reduce the grill heat to medium and grill an additional 3-5 minutes per side with the lid CLOSED, depending on your desired final temperature (see notes).
Charcoal Grill: Place the steaks on the grill over direct heat. Sear the steaks 2 minutes with the lid OPEN, flip the steaks, then sear 2 minutes more. Move the steaks away from direct heat; grill an additional 3-5 minutes per side with the lid CLOSED, depending on your desired final temperature (see notes).
Remove the steaks from the grill and transfer to a cutting board. Rest 10 minutes, then slice against the grain.
Notes
TEMPERATURE GUIDE: Flat iron is a very tender cut that quickly loses flavor and texture the longer it cooks. Pull the steaks once the internal temperature registers no higher than 130°F.
RARE: cook to 120°F, rest 5 minutes; final temperature will rise to approximately 125°F.
MEDIUM RARE: cook to 125°F, rest 5 minutes; final temperature will rise to approximately 130°F.
MEDIUM: cook to 130°F, rest 5 minutes; final temperature will rise to approximately 135°F.