Grilled Flat Iron with Cowboy Butter

Cooking flat iron steak on the grill and then dipping each bite in delectable cowboy butter is a carnivore bliss. This easy recipe puts you in charge of recreating the experience.

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Our Easy Grilled Flat Iron Steak Recipe

This preparation is the perfect testament to the virtues of simply grilling a great cut of beef to bring out the best it has to offer. The richly flavored but lean meat of flat iron steak welcomes butter based steak sauces or garlic herb compound butter. We especially like to pair it with the cowboy butter dipping sauce presented below. 

What is Flat Iron Steak?

Flat iron is a narrow steak harvested from the chuck primal cut (aka the beef shoulder) and sits protected on both sides by bones.

The larger meat cut that contains it is traditionally known as top blade roast. It consists of the infraspinatus muscle which is bisected by a thick layer of connective tissue. This large swath of tough fascia provides a lot of support to the animal. In result the two sides of the muscle do not work much and the meat is lean and tender.

Cutting a Flat Iron Steak

The top blade roast is quite difficult to denude but the results are worth it. 

To cut a flat iron steak the butcher removes the connective tissue in the middle. Once this is done the two resulting pieces of the infraspinatus muscle are treated separately.

One piece, which is thicker and almost perfectly shaped as a rectangle looks like an old fashioned flat iron – hence the name of the steak.

The other one, a bit longer and thinner, is either called the same way or called top blade steak. It really depends on the style practiced by the butcher.  

Other names for flat iron steak are top blade filet and shoulder top blade steak. 

Is Flat Iron Steak Tender?

Flat iron steak is one of the most tender beef cuts due to the reasons described above. Many butchers argue it is second only to beef tenderloin (filet mignon). 

How is Flat Iron Steak Best Cooked?

The best ways to cook a flat iron steak involve high-heat and short times due to its lack of fat marbling. 

This is why flat iron steak is perfect for grilling or searing in a screaming hot pan (pan-frying). 

The relative thinness of the steak also makes it a great candidate for marinades, similarly to flank steak. We like to use a marinade when pan-frying it, while simply seasoning it with salt or a dry rub is our preference when grilling it.

How to Cook Flat Iron Steak on Grill: Step-by-Step

To grill a perfect flat iron steak you have to make sure that you do not overcook it while giving it a good outside sear. 

To that end you will need to get your grill really hot and place the steak over direct heat. This applies to both gas grills and charcoal grills. If you have a searing side burner/sear box as part of your grilling set up – it is ideal for a super hot fast sear such as desired with a flat iron cut (shown below).

Prep. Season your steak with either only salt or a spice mix of your choosing. 

Grill. Set it over screaming hot, clean and lightly oiled grill grates. Sear the first side for about 5 minutes and then flip it over. Grill the second side until it reaches the temperature of your desired doneness (likely less than 4-5 minutes). See the recommended temperatures below.

Rest and slice. Rest the steak for 5 minutes, you may loosely cover it with foil. Slice it thinly against the grain for a tender bite. 

Cooking Tips

• If you have the time leave the seasoned steak in the refrigerator for a few hours in order for the salt to penetrate the surface and flavor it better. This will also help with better crust formation.
• Before you cook it you do not need to let it come to room temperature (it is too thin and narrow). A cool steak is best in this case.
• Flat iron steak is best cooked medium-rare. This is optimal for both juiciness and meat texture. Do not cause it to dry out and become tough by overcooking it. 

Temperature Chart for Grilling Flat Iron Steak

Use a meat thermometer to take temperature and pull the steak off the grill a bit earlier than the desired doneness as it will continue to cook while resting. 

RARE : stop cooking when 115-120 F | final serving temperature reaches 120-125 F
MEDIUM-RARE : stop cooking when 120-125 F | final serving temperature reaches 125-130 F
MEDIUM : stop cooking when 130-135 F | final serving temperature reaches 135-140 F

Flat Iron Steaks on Grill Love Butter Sauces

While both very juicy and flavorful this grilled beef steak gets even better when paired with butter rich dipping sauce such as Garlic Butter Sauce or the cowboy butter shown below.  

How to Make Cowboy Butter Dipping Sauce for Steak

Here is a quick step-by-step visual of the workflow for our cowboy butter recipe. It is simply a broken butter sauce with several flavorful ingredients added.

Gather & prep. You will need good quality unsalted butter, fresh parsely & thyme, minced garlic, finely chopped shallot (or red or sweet onion), Dijon mustard, lemon juice, Worcestershire sauce, red pepper flakes, kosher salt and black pepper. 

Make. Over medium heat in a small skillet melt about two tablespoons of butter and saute the shallot, garlic and thyme. Once soft stir in the mustard and Worcestershire, then add lemon juice. Finish by adding the remaining butter and chopped parsley. Once the butter has melted the sauce is ready to serve.

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Grilled Flat Iron Steak with Cowboy Butter

Yield: 4 servings

Prep Time: 2 minutes

Cook Time: 10 minutes

Total Time: 12 minutes

A fast sear over direct heat and a brief resting period are all that is needed to prepare the perfect grilled flat iron steak. Try the cowboy butter dipping sauce to add richness to the tender, but lean meat.

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Ingredients

Grilled Flat Iron Steak

• 1.5 lbs flat iron steak
• kosher salt (to taste) or steak seasoning (to taste)
• 1 tbsp cooking oil (such as canola or sunflower*)

Cowboy Butter

• 1 stick butter (8 tbsp)
• 1 tbsp shallot, finely diced
• 1-2 cloves garlic, minced
• 1 tsp fresh thyme leaves
• 1 tbsp Dijon mustard
• 1/2 tbsp Worcestershire sauce (or to taste)
• 1 tbsp lemon juice (or to taste)
• 1 tsp red pepper flakes (or to taste)
• 1 tbsp fresh parsley, finely chopped
• kosher salt and black pepper, to taste

Instructions

Grilled Flat Iron Steak

1. Season the steak with kosher salt or steak seasoning of your choice. If you have the time let sit refrigerated for the salt to better penetrate the surface. When ready to grill make sure the steak is cool, not at room temperature.
2. Clean and lightly grease grill grates. Preheat the grill (charcoal or gas) to very hot (about 500 F). If it has a searing side burner/sear box use that instead.
3. Place the steak over direct heat and cook for 5 minutes on one side. Flip over and cook until the internal temperature of your desired doneness is reached. About 4 minutes, most likely less for medium-rare. (Use a meat thermometer and consult the temperature ranges provided below.)
4. Rest the flat iron for about 5 minutes before you slice it against the grain. (You may loosely tent it with foil.) Serve with cowboy butter.

Cowboy Butter

1. Heat a small skillet over medium heat. Melt 2 tablespoons of the butter and saute the shallot, garlic and thyme until soft, 2-3 minutes.
2. Stir in the mustard and Worcestershire sauce, then add lemon juice and red pepper flakes.
3. Add the remaining butter (cut in pieces is helpful) and chopped parsley. Once the butter has melted transfer to a bowl and serve the sauce.

Notes

*Use oil with high smoking point to grease the grill grates and (optional) brush a bit over the flat iron steak before grilling.

The exact time for grilling the second side of the steak depends on its thickness and size, as well as your desired doneness. Use a meat thermometer to take temperature.

RARE : stop cooking when 115-120 F | final serving temperature reaches 120-125 F

MEDIUM-RARE : stop cooking when 120-125 F | final serving temperature reaches 125-130 F

MEDIUM : stop cooking when 130-135 F | final serving temperature reaches 135-140 F

It is best to make the cowboy butter just before you grill the steak and then keep it warm. Or if you have someone to help you have them work on the butter while you are cooking the flat iron and allowing it to rest.

Nutrition Information:

Yield: 4 Serving Size: 1
Amount Per Serving: Calories: 625Total Fat: 48gSaturated Fat: 23gTrans Fat: 2gUnsaturated Fat: 20gCholesterol: 202mgSodium: 636mgCarbohydrates: 3gFiber: 1gSugar: 1gProtein: 43g

Nutritional information includes the very rich cowboy butter sauce.

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