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Flat Iron Steak Fajitas

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Need a quick and delicious dinner idea? Then try these flat iron steak fajitas made with tender steak, fresh bell peppers, and sweet onions!

Fiesta Friday is a mainstay in our household. But, there’s only so many tacos you can eat before you want something new.

For today’s recipe, we’re sharing our flat iron steak fajitas using our homemade fajita seasoning, or a store-bought one if you prefer, and flat iron steak.

The best part about this recipe is that it only uses one pan; a skillet. Which is great for clean-up.

Four flat iron steak fajitas served with fresh limes.
Kim and I love to serve our fajitas with fresh limes!

How to make flat iron steak fajitas in a slow cooker?

You can make this recipe in your slow cooker. All you need to do is add the beef, peppers, onions, and seasoning to your appliance.

Then, add a 1-2 cups of beef broth to the cooker. That’s the only change you need to make to the ingredients. Set it on low heat for about 4 hours (or 2-2.5 hours on high).

Once the fajitas are done, serve them with your favorite condiments like sour cream, Monterrey Jack Cheese, and pickled or fresh jalapenos.

If you prefer chicken, then try our slow cooker chicken tacos. The recipes are very similar in design and ingredients.

The cooked beef, peppers, and onions in the cast iron skillet.
Kim used our gas stove-top to char the tortillas before serving.

How to make fajitas in a cast iron skillet?

First, start by slicing the flat iron steak into strips. Make sure to cut against the grain of the beef.

After that, toss the meat and fajita seasoning together in a mixing bowl. The beef should be evenly coated before moving on.

The spices and beef tossed together in a bowl.
For a twist on this recipe, try using thinly cut sirloin steak.

Next, slice the bell peppers and onions into strips. Grab another mixing bowl and toss the vegetables with more seasoning.

Then, place a large skillet over medium to medium-high heat and let the pan get warm.

Fajita seasoning being sprinkled over a bowl of sliced peppers and onions.
Try using a mix of green and red bell peppers to add a touch of color to the earthy dish.

Afterward, add in the oil and vegetables. Be careful, the pan will be hot at this point. Let the peppers and onions cook for 3-4 minutes.

When they start soften around the edges, add the beef and let the mixture cook for about 5-minutes or until the steak is done to your likeness.

Top-down view of the beef and vegetables in the skillet
There’s just something about a sizzling cast iron pan loaded with meat and veggies.

Last, remove the pan from the heat and serve with warm tortillas. Occasionally, I serve mine with this corn and black bean salsa. It adds a ton of flavors and textures!

That’s it, your flat iron steak fajitas are done. Kim and I hope you enjoy this meal and wish you all the best 🙂

Looking for another way to flavor steak? Then, check out our beef beer marinade recipe.

Up-close view of a fajita served with a lime wedge.
All this fajita needs is a dollop of sour cream.

Recipe Tips:

  • Make sure your skillet is hot before cooking the steak and vegetables. The meat will get a good sear and the peppers and onions will char a little bringing out the natural sugars.
  • I would only tenderize the fajita meat if it lacks proper fat marbling. You want a good amount of fat in the steak to keep it tender and juicy. Otherwise, you may want to tenderize it before getting started.
  • To add extra flavor to the dish, consider charring or steaming your tortillas just before serving.

Is flat iron steak tough?

Usually, the meat has enough marbling to stay tender. However, if it’s poorly cooked, then it will become chewy and tough.

Why is my fajita meat tough?

Probably because it was overcooked. Flat iron steak is still steak and needs to be treated like one. Try to cook it in whole pieces, medium doneness, and let it rest for a few minutes before cutting.

Up-close view of a fajita served with a halved lime.

Flat Iron Steak Fajitas

Yield: 4 Servings
Prep Time: 15 minutes
Cook Time: 10 minutes
Total Time: 25 minutes

Need a quick and delicious dinner idea? Then try these flat iron steak fajitas made with tender steak, fresh bell peppers, and sweet onions!


  • 16 Ounces Flat Iron Steak, (or flank steak or Hangar steak, cut into strips)
  • 1 Large Green Bell Pepper, (cut into strips)
  • 1 Large Red Bell Pepper, (cut into strips)
  • 1 Small White Onion, (cut into strips)
  • 1 1/2 Tablespoons Fajita Seasoning, (separated)
  • 1 Tablespoon Cooking Oil, (canola or vegetable)
  • 8 Small Tortillas


  1. In a small bowl, combine the sliced steak and 1 tablespoon of fajita seasoning. Toss the two together until all pieces of steak are evenly coated with seasoning. Set aside.
  2. In a separate medium bowl, combine the vegetables and remaining ½ tablespoon of fajita seasoning. Toss to combine.
  3. Heat a large skillet or flat iron griddle over medium - high heat. When the skillet is hot, add the oil and the vegetables. Cook for 3 to 4 minutes just until the vegetables begin to soften around the edges. Add the strips of steak and meat with the vegetables while stirring frequently. Cook for 4 to 6 minutes or until desired doneness is reached.
  4. Remove from the pan, and serve with warm tortillas, guacamole, and sour cream.


The calories listed are an approximation based on the ingredients in the recipe card and a 4-ounce serving (two small fajitas). Actual calories will vary. Leftovers can be stored in a sealed container, in your fridge, for up to 3-days.

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As an Amazon Associate and member of other affiliate programs, I earn from qualifying purchases.

Nutrition Information:
Yield: 4 Serving Size: 4 Ounces
Amount Per Serving: Calories: 441Total Fat: 20gSaturated Fat: 6gUnsaturated Fat: 0gCholesterol: 75mgSodium: 575mgCarbohydrates: 37gFiber: 3gSugar: 6gProtein: 27g

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