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Slow Cooker Flank Steak

5 from 2 votes

Updated: · Published: by

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Servings 6 servings
Prep 15 minutes
Cook 6 hours

This Slow Cooker Flank Steak recipe is perfect for a busy weeknight dinner or a cozy Sunday meal with the family. Tender and juicy flank steak made in the slow cooker.

Flank steak recipe in a slow cooker.

The best part? You can set it and forget it while your house fills with mouth-watering aromas.

Looking for specifics on the recipe? Use the table of contents to click on sections of the recipe.

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Why you'll love this recipe

🧾 Ingredient List

Slow Cooker Flank Steak ingredients with text overlay.

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  • beef flank steak
  • chili powder
  • garlic powder
  • granulated white sugar
  • salt
  • black pepper
  • olive oil
  • red wine vinegar
  • Dijon mustard
  • yellow onion

Equipment

  • Ninja 8-1 Slow Cooker
  • Cutting Board
  • knife
  • Measuring Spoons and Cups

Instructions

This is an overview of the recipe. The full instructions are below in the recipe card.

A raw flank steak seasoned with salt, pepper, and chili powder to be cooked in the slow cooker.
  1. Season the flank steak well on both sides. Lightly pat the seasonings into the meat.
A browned flank steak in a cast iron skillet ready to be placed in a slow cooker.
  1. Sear the steak in a hot skillet on both sides for 3 minutes per side.
Slow cooker with sliced onions in the vessel.
  1. Add the onions to the bottom of the slow cooker.
A flank steak that has been browned on top of sliced onions with red wine vinegar in the slow cooker.
  1. Place the browned steak to the slow cooker on top of the onions. Pour the red wine vinegar into the skillet, scraping to remove any stuck-on pieces. Mix in the Dijon mustard with the red wine vinegar. Pour the sauce over the steak.
A flank steak in the vessel of a crock pot after it has cooked for 4 hours.
  1. Place the lid on the slow cooker. and cook on low for 4 hours. The meat will be tender and cooked through. Transfer to the cutting board, and let the steak rest for 10 minutes.
Sliced flank steak in its juices topped with sliced cooked onions in the vessel of a slow cooker.
  1. Slice the steak against the grain, and then return the steak to the slow cooker or serve on a platter with the onions and juices.
Sliced flank steak made in the slow cooker on a plate with mashed potatoes.

Eileen's Tips for Success

  • One of my favorite garnishes for this tender meat is a sprinkle of sliced green onions and a squeeze of fresh lime juice for a delicious flavor.
  • Leftovers make delicious tacos with Pico de Gallo, Tomatillo Salsa, and guacamole.
  • If you want to make a gravy to top mashed potatoes, rice, or noodles, add a cornstarch slurry to the slow cooker juices and cook until the sauce thickens. 

Variations

Do you want to change up this recipe? Here are some ways that you increase the flavor of this dish.

  • Spice: Add a can of diced tomatoes with green chilies for spice.
  • Herbs: Add any fresh herbs in season.
  • Garlic: Add fresh chopped garlic to the slow cooker vessel.
  • Umami: A dash of soy sauce or Worcestershire sauce can add a rich flavor to the juices.
  • Gravy: To make gravy, mix cornstarch with cold water and add to the slow cooker to thicken the sauce.

Make-ahead, storage, and freezer tips

Make ahead - One great thing about this recipe is that it makes for great leftovers. So, feel free to reheat it ahead and just reheat it when you are ready to enjoy it. 

Storage - Store leftover flank steak in an airtight container in the fridge for 3-4 days. 

Freezing -  This dish can also be frozen for longer storage. Let it cool completely before transferring it to a freezer-safe container. 

A white plate with a cooked flank steak that was made in the crockpot.

Frequently Asked Questions

What's the best way to reheat crock pot flank steak?

The best way to reheat flank steak made in the slow cooker is to place it in a skillet or on a baking sheet and heat it in the oven at 350 degrees Fahrenheit for about 10-15 minutes, or until heated through. You could also reheat it in the microwave by eating it for 1-2 minutes.

Can I use a different type of steak for this recipe?

Yes, you can use other cuts of beef, such as sirloin steak, London broil, or skirt steak. Adjust the cooking time accordingly, as these cuts may cook faster than flank steak.

​Can you add raw steak to a slow cooker?

Yes, however, for this recipe, I recommend searing the steak first because it will give you the best flavor. 

Serving Suggestions

See all our side dishes here.

Similar recipes

Check out all Slow Cooker recipes.

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Eileen  xo

If you click on the number of servings in the recipe card, you can adjust the measurements up or down for the exact number of servings you need.

Made this recipe, please give it a review and 5 stars! ⭐️⭐️⭐️⭐️⭐️

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A slow cooker with sliced flank steak topped with carmelized onions.
Eileen Murphy Kelly

Slow Cooker Flank Steak

5 from 2 votes
Slow Cooker Flank Steak is an easy recipe for a delicious steak dinner with tender and juicy flank steak, every time.
Print Recipe Pin Recipe
Prep Time 15 minutes
Cook Time 6 hours
rest time 10 minutes
Total Time 6 hours 25 minutes
Servings: 6 servings
Course: Main Course
Cuisine: American
Calories: 240
Ingredients Equipment Method Nutrition Notes

Equipment

Ingredients
  

Instructions
 

  1. Season the 2 pound flank steak with 1 teaspoon chili powder, 1 teaspoon garlic powder, ½ teaspoon granulated sugar, ½ teaspoon kosher salt, and ½ teaspoon black pepper
  2. Heat a heavy skillet or cast-iron pan over medium-high heat. Add 1 Tablespoon olive oil and swirl around the skillet. Add the seasoned flank steak to the skillet and cook until browned, about 3 minutes per side.
  3. While the steak is browning, spread 1 cup yellow onion (peeled and sliced thin) in the bottom of the slow cooker.
  4. When the steak is browned on both sides, transfer the steak to the slow cooker and place it on top of the sliced onions.
  5. Pour 2 Tablespoons red wine vinegar into the skillet, scraping to pull up any brown bits. Whisk in ½ teaspoon Dijon mustardinto the skillet to blend with red wine vinegar. Pour the sauce over the steak.
  6. Place the lid on the slow cooker. Cook on low for 4 hours. The meat will be tender and cooked through.
  7. Transfer the steak to a cutting board. Let the steak rest for 10 minutes. Thinly slice the steak, against the grain. Serve with the onions and juices from the pan.
  8. Serve with your favorite sides like mashed potatoes, green beans, or potato salad.

Nutrition

Serving: 1servingCalories: 240kcalCarbohydrates: 3gProtein: 33gFat: 10gSaturated Fat: 3gPolyunsaturated Fat: 1gMonounsaturated Fat: 5gCholesterol: 91mgSodium: 281mgPotassium: 559mgFiber: 1gSugar: 1gVitamin A: 100IUVitamin C: 1mgCalcium: 39mgIron: 3mg

Notes

Tips and FAQs above with important tips and questions that can help make a delicious recipe. 
Note 1: This recipe works well with a London broil. 
Note 2: 1 cup of onion is about 1 medium-sized yellow onion.
 
I'm not a registered dietician, I do my best to provide the most accurate nutritional values. Any nutritional data I provide is an approximation. Actual dietary information can vary based on ingredients and portion sizes. 
 
 

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If you loved this recipe, please leave a ⭐⭐⭐⭐⭐ rating below — it helps other find it and means the world to me! — Eileen xo 🍀

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  1. Juyali

    5 stars
    I love flank steak, but it always turned out so tough for me.
    This slow-cooked version is a revelation! It was tender and so juicy.
    It made a very nice meal for our family, and I'll be making this again. Thanks!

    Reply

    • Eileen Murphy Kelly

      Thank you for letting me know you much you enjoyed the flank steak. Making it in the slow cooker is so easy with the most juicy and tender results.

      Reply

  2. Tom Keller

    5 stars
    I made this steak in the slow cooker - perfection. Very juicy and tender. It’s been so hot - we didn’t want to grill. I’ll be making my flank steak and London broil in the slow cooker from now on

    Reply