Crock Pot Flat Iron Steak with Portobello Mushrooms & Potatoes

Easy and delicious flat iron steak done in the slow cooker with portobello mushrooms and potatoes, 
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How to Make delicious Crock Pot Flat Iron Steak with Portobello Mushrooms & Potatoes! This dinner cooks low and slow and turns a tough steak into melt-in-your=mouth perfection!

Crock Pot Flat Iron Steak with Portobello Mushrooms & Potatoes in a white plate

Easy Flat Iron Steak Recipe

It snowed this week and while you may think that’s nothing, to me it was Mother Nature (or the Alberta weather) letting us know that she ain’t done with us yet. Oh, we may have had the mildest winter that I can ever remember, with very little snow and days so nice that I’ve lived in a sweater instead of a winter coat for weeks upon end, but it’s not over until Mother Nature says so. And she usually says so right after she dumps a large amount of  snow on us for the May long weekend.

We’re still quite a few weeks away from May long weekend, so as much as I had enjoyed my BBQ (and the snow-free deck that it sits on) it’s STILL crock pot weather. It’s still the comforting, hot-food-that-cooks-all-day time of year, so I thought I’d try crock pot flat iron steak.

ingredients for Flat Iron Steak all set in a marble tableWhat is Flat Iron Steak?

Flat iron steak is a cut of beef that comes right off of the shoulder-blade area of the cow. This thin strip of steak is a tender, lovely piece of beef that I prefer to cook low and slow, contrary to popular use. The flat iron has come back in style lately, with a lot of restaurants serving it up along with flank and hanger steaks. Sadly, it’s very hard to get one properly cooked and sliced. I am getting cranky in my old age and to be honest, there are very few cuts of steak that I enjoy as a grilled item anymore. I know. Forty is when the descent into senior-ism starts.

However I am completely serious, all jokes aside. Trendy or not, I’ll take a tenderloin for the BBQ and skip everything else. That sounds really hoity-toity (have I ever used that phrase here? Well, it’s about time I did) but for the very few times we that actually eat steak, it’s not that bad.  Go for small portioned, good quality steak for grilling every time and you will be a happy griller.

Flat iron steak does not have to be fancy. It doesn’t always need a chimichurri – although it really is my favorite way to eat flank steak- and it doesn’t need 11 herbs and spices.

I stopped by ACME Meat Market here in Edmonton, the perfect place to pick up cuts of meat that you won’t find at your regular grocery store. You can see with the meat how it will be better when you cook it low and slow. See all that fat marbling?

fresh Flat Iron Steak with a fork beside it

How to Cook Flat Iron Steak

This was the simplest recipe that I could possibly think of and it is scrumptious. Crock pot Flat Iron steak is SO the way to go!It will dissolve with the right amount of cooking time, leaving you with meat reminiscent of short ribs. Falls apart and into your mouth. Low and slow is meant for the slow cooker, and so are large chunks of onion and massive portobello mushroom along with the flat iron steak.

  • Place the ingredients into the crock pot in the correct order
  • Cook the flat iron steak low and slow for hours
  • Serve and enjoy
a plate of Flat Iron Steak with Portobello Mushrooms & Potatoes ready to be enjoy!

The flat iron steak cooks the best when it is placed under the vegetables and cooks with lots of liquid from the beef broth and the vegetables on top that are releasing liquid as well.

Crockpot with Flat Iron Steak, Portobello Mushrooms, Potatoes and beef broth ready for cooking

This right here?

close up Flat Iron Steak with Portobello Mushrooms & Potatoes in a white plate

Dinner perfection.

It’s such a comforting dish, with simple yet delicious flavours, which is my favorite kind of meal. Prep it, set it, let it cook all day and then come home to a hot, delicious meal ready to go.

Happy Cooking everyone! How’s the weather been where you live? How was your winter?

Love you more than chocolate,


Crock Pot Flat Iron Steak with Portobello Mushrooms and Potatoes

Easy and delicious flat iron steak done in the slow cooker with portobello mushrooms and potatoes, 
5 from 28 votes
Prep Time
10 minutes
Cook Time
8 hours
Main Course
Slow Cooker / Crockpot
Karlynn Johnston


  • 2-3 pounds of flat iron steak
  • 1 pound of sliced portobello mushrooms
  • 1 cup beef broth
  • 1 large white onion sliced into large rings
  • 3-4 large red potatoes washed and chopped into 1 pieces with skin still on
  • butter for greasing crockpot


  • Grease the interior of your crockpot with a generous amount of butter.
  • Place the flat iron in the bottom of the crockpot.
  • Place the vegetables on top, then pour the beef broth over the top.
  • Cook on low for 6-8 hours, until the potatoes are tender.
  • Serve and enjoy!

Nutrition Information

Calories: 436kcal, Carbohydrates: 7g, Protein: 45g, Fat: 24g, Saturated Fat: 9g, Cholesterol: 149mg, Sodium: 180mg, Potassium: 1153mg, Fiber: 1g, Sugar: 4g, Vitamin C: 2.1mg, Calcium: 23mg, Iron: 5.8mg

All calories and info are based on a third party calculator and are only an estimate. Actual nutritional info will vary with brands used, your measuring methods, portion sizes and more.

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Karlynn Johnston

I’m a busy mom of two, wife & cookbook author who loves creating fast, fresh meals for my little family on the Canadian prairies. Karlynn Facts: I'm allergic to broccoli. I've never met a cocktail that I didn't like. I would rather burn down my house than clean it. Most of all, I love helping YOU get dinner ready because there's nothing more important than connecting with our loved ones around the dinner table!

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Reader Interactions

Comments & Recipe Tips Share a tip or comment!

  1. Joan Wesolosky says

    This recipe looks interesting. Should the broth completely cover the ingredients in the crock pot?

  2. Gary Comer says

    I pressure cook in small jars for even faster meals, survival too. 941#

  3. Christine Scott says

    Think I could use flank steak, I have a 3 lb piece. Since you told Sophie yrs ago she could use another type of steak, I think it might be fine.



  4. Karen Anfenson says

    Best recipe for flay iron steak I have ever had!!
    I have used it in the crockpot before, but NOTHING a is better that this recipe ever,
    our favorite way to cook this great piece of meat!!

  5. Ellie says

    This looks awesome! Can you use sweet potato instead of white potato? I’m not able to have nightshade vegetables. Thanks!

    • Nancy L Fischer says

      I’m making it for dinner tonight I did not have an onion but I had pearl onions so I’m using pearl onions and red potatoes hope it’s good I will let you know

  6. Richard Huckle says

    Your Flat Iron steak recipe via slow cooker/crock-pot is perfect now that I have found a supplier of this type of steak cut at Morrisons in the UK.
    Much appreciated !5 stars

  7. Sheryl B says

    This was so easy, who would think you can make steak in a slow cooker? It’s not really something that common, but I will make this from now on. Tender and flavorful.5 stars

    • Sophie Nakoneczny says

      Have you ever made it with another type of steak?

    • The Kitchen Magpie says

      Sophie Nakoneczny as long as it’s a steak that has marbled fat or does well when cooked a long time (chuck or blade!) you are good to go!

5 from 28 votes (25 ratings without comment)

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