Sous Vide Flat Iron Steak is an easy and foolproof recipe to cook this affordable cut, delivering intense beef flavor with a very tender texture. Cooking it to a precise temperature in the sous vide water bath and finishing with a quick pan sear produce the best result. 

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What Is Sous Vide?

You may have heard of the French cooking method called sous vide. Translating as “under vacuum”, this process involves vacuum-sealing food and slow-cooking in a water bath at a precisely controlled temperature. After hours of cooking, the food comes out more tender and flavorful than with most other methods.

Why This Recipe Works

With traditional cooking methods like grilling, pan-searing, or broiling, there’s a very small window of the perfect doneness when making flat iron steaks. If you miss that window, the meat will become tough and chewy. 

Sous vide cooking guarantees the result and ensures the steak is perfectly cooked by using precise temperature control. It also produces the meat with even doneness edge-to-edge.

Equipment You’ll Need

• Sous Vide Immersion Circulator
• Zip-loc Bags
• Kitchen Tongs

Ingredients

• Flat Iron Steak: This cut is considered to be very tender, second only to filet mignon in tenderness. It comes from the top blade which has a lot of flavorful marbling with uniform thickness, and is less expensive than other tender beef cuts like rib eye or New York strip steak. This particular cut is flat-looking with great flavor, similar to flank steak, skirt steak, and hanger steak. 
• Olive Oil: Regular olive oil works the best for this recipe. Avoid extra virgin olive oil as it has a lower smoke point.
• Salt & Pepper: I used coarse salt, but you can use regular table salt or sea salt. Freshly ground black pepper works the best.
• Garlic Powder: I used garlic powder for this recipe, but you can also use freshly minced garlic.

Flat Iron Steak Seasoning/Marinade

A simple seasoning made of salt, pepper, and garlic powder can bring out the best natural flavor of the flat iron steak. Alternatively, flat iron steak is also a good candidate for a marinade as it’s relatively thin, and the flavor can penetrate into the meat easily. 

Pro Tips: It’s important to season generously before sous vide cooking for the best result! 

Step-By-Step Instructions

Step 1: Pre-heat sous vide machine and season the steak

Set the Sous Vide Precision Cooker to 135°F (57°C) for medium-rare doneness.

Season the steak with salt, pepper, and garlic powder.

Step 2: Vacuum seal and sous vide

Place the seasoned flat iron steak in a zip-lock bag and vacuum seal it using the “water displacement”  technique. (You can use a vacuum sealer if you have one.)

Place the bag in the sous vide water bath and cook for 2 hours.

Step 3: Sear

When the timer goes off, remove the bag from the water and transfer it to an ice bath or the refrigerator. Let it chill for about 10 minutes. Pat dry the flat iron steak with paper towels. Add more seasoning if needed. (It’s important to wipe off any extra moisture as it inhibits proper searing.)

Then grill or sear for about 1 minute per side, just to caramelize the outside. 

Sous Vide Flat Iron Temperature And Time Chart

I recommend cooking flat iron steak at 135°F (57°C) for medium-rare doneness. If you’d like to have a tender, juicy flat iron steak, don’t cook the meat past medium doneness. If you’d like to try other temperatures, follow the chart below:

Steak Doneness	Temperature
Rare	125°F (52°C)
Medium Rare	135°F (57°C)
Medium	140°F (60°C)
Medium-well	155°F (68°C)
Well Done	165°F (73°C)

Flat iron steak requires longer cook time than most other tender cuts, and I recommend cooking it for 2 hours. 

Pro Tip: It’s fine to leave it in the warm bath for an extra 30-60 minutes. But avoid cooking it for too long as the texture could become mushy.

Tips For Vacuum-Sealing The Steak Without A Vacuum Sealer

If you don’t have a vacuum sealer, a regular zip-top bag works well with this recipe. The trick is called water displacement technique: just place the seasoned steak in a zip-top bag, and seal all but one corner of the bag. Slowly place it into a bowl with cold water, making sure everything below the zip-line is covered by water. Then seal the rest of the bag (You can watch the video in the recipe card for a visual tutorial).

Serving Suggestions

Serve them with side dishes like Fruit Salsa, Steamed Broccoli, or Sous Vide Potatoes for an amazing meal! Some other sides that I like to pair with this recipe include:

• Asparagus
• Mashed Potatoes
• Carrots

Finishing After Sous Vide Cooking For A Caramelized Crust

While flat iron steak comes out of sous vide mouthwateringly tender, it benefits from searing to create a caramelized crust. You can use a hot skillet, grill or the broiler. My favorite is cast iron skillet.

First, heat your skillet until very hot. While you’re waiting, pat the steak dry using paper towels to remove excess moisture that will interfere with searing. 

You’ll also want to rub it all over with a high smoke point oil. Now you can use kitchen tongs to place the steak on the heat to sear for 1 to 2 minutes until browned. Flip and sear 1 to 2 minutes more. It’s now ready to serve!

Side Dishes To Serve With Flat Iron Steak

• Mashed Potatoes
• Sweet Potatoes
• Potatoes
• Carrots
• Broccoli

FAQs

Can I sous vide frozen flat iron steak?

Yes! Follow the same instruction and cook the frozen steak 30 more minutes in the warm water bath.

Is a flat iron steak a tough cut?

A flat iron steak is not considered a tough cut. In fact, it has a solid tenderness rating of 8/10. With sous vide cooking, a flat iron steak comes out extremely tender and flavorful.

Can I sous vide flat iron steak longer than the recommended time?

Yes, you can extend the cooking time for flat iron steak by an hour or two no problem. Just avoid leaving it for long periods or overnight, as the texture will start to deteriorate and become mushy.

More Sous Vide Steak Recipes

• Sous Vide Sirloin Steak
• Sous Vide T-Bone Steak
• Sous Vide New York Strip
• Sous Vide Tri Tip

UPDATED JULY 14, 2020: This post was originally published on May 15, 2020. We spiffed it up and added a brand new video to make it sparkle!