Dinner · Part 3 of 3: Tips & recipe card

Cowboy Butter Flank Steak Slow Cooker Dinner Tips, FAQ & printable recipe

Name: Cowboy Butter Flank Steak Slow Cooker Dinner
Prep time: 10 min
Cook time: 6 h
Total time: 6 h 20 min
Cuisine: American
Ingredients: 2 lb flank steak, thinly sliced against the grain; 1 cup peeled pearl onions; 2 cups crinkle-cut carrots; 2 sticks garlic-herb cowboy butter (store-bought or homemade); 1 oz dry au jus mix

By Clara Weller · Oct 28, 2026

Slow cooker flank steak with pearl onions and carrots in a rich au jus, served in the crockpot.

Prep: 10 min
Cook: 6 h
Total: 6 h 20 min
Serves: 6

Includes 10 min resting

Tips for success

For extra depth of flavor, sear the flank steak strips in a hot skillet with a little oil before adding them to the slow cooker.

This adds a rich, caramelized crust that enhances the final dish. If you're short on time, skip this step—the slow cooker will still produce delicious results.

To make the sauce even more luxurious, stir in a tablespoon of cold butter just before serving. This emulsifies the sauce and gives it a glossy sheen.

For a thicker sauce, mix a tablespoon of cornstarch with two tablespoons of cold water, then whisk it into the slow cooker during the last 30 minutes of cooking.

Variations

Spicy Cowboy Butter: Add 1-2 teaspoons of chopped chipotle peppers in adobo sauce to the butter before adding to the slow cooker. This adds a smoky heat that pairs beautifully with the beef and sweet vegetables.
Mushroom and Onion: Replace the carrots with 8 ounces of sliced cremini mushrooms. Add them along with the pearl onions for an earthy, savory twist that complements the beef and au jus.
Red Wine Au Jus: Replace 1/2 cup of the water with dry red wine when making the au jus. The wine adds depth and complexity to the sauce, making it even more luxurious.
Herb-Infused Butter: If you can't find cowboy butter, make your own by mixing 1/2 cup softened butter with 2 cloves minced garlic, 1 tablespoon chopped fresh parsley, 1 teaspoon dried thyme, and a pinch of red pepper flakes.

Storage and make-ahead

Fridge: Store leftovers in an airtight container in the fridge for up to 4 days. Reheat gently in a saucepan over low heat, adding a splash of broth if needed.
Freezer: Freeze cooled leftovers in a freezer-safe container for up to 3 months. Thaw overnight in the fridge before reheating.
Reheat: Reheat gently on the stovetop over medium-low heat, stirring occasionally, until warmed through.

Store any leftovers in an airtight container in the refrigerator for up to 4 days. The beef will continue to absorb the sauce, so it may become even more flavorful.

Reheat gently on the stovetop or in the microwave, adding a splash of beef broth or water if the sauce has thickened too much.

This recipe is perfect for meal prep. Assemble all the ingredients in the slow cooker insert the night before, cover, and refrigerate.

The next morning, place the insert in the slow cooker and cook as directed. You can also cook the full recipe ahead of time and refrigerate it for up to 3 days; reheat gently on the stovetop before serving.

Serving ideas

Serve the beef and vegetables over creamy mashed potatoes, egg noodles, or polenta. The rich au jus is perfect for spooning over the top, and a sprinkling of fresh parsley adds a pop of color. For a low-carb option, serve over cauliflower mash or alongside roasted vegetables.

This dish also makes a great filling for sandwiches or tacos. Pile the beef onto crusty rolls and top with provolone or mozzarella, then broil until the cheese melts. Or serve in warm tortillas with a drizzle of the au jus and a dollop of sour cream.

Frequently asked questions

Can this recipe be made with a different cut of beef?

Yes, you can use sirloin, chuck roast, or even round steak. Just slice it thinly against the grain. Chuck roast will become even more tender as it cooks, but it may need a slightly longer cooking time. Adjust the cooking time as needed until the beef is fork-tender.

What is cowboy butter and where can it be found?

Cowboy butter is a flavored butter typically made with garlic, herbs, and sometimes a bit of heat. It's often sold in the dairy section of supermarkets, near other specialty butters. You can also make your own by mixing softened butter with minced garlic, chopped herbs like parsley and chives, and a pinch of cayenne or paprika.

Can this dish be cooked on high instead of low?

Yes, you can cook it on HIGH for 3 to 4 hours instead of LOW for 6 to 7 hours. The results will be similar, but the beef may be slightly less tender. Check for doneness at the minimum time and continue cooking if needed.

How can the sauce be thickened?

If the sauce is too thin, mix 1 tablespoon of cornstarch with 2 tablespoons of cold water until smooth, then stir into the slow cooker during the last 30 minutes of cooking. Let it simmer until the sauce thickens. Alternatively, you can remove the beef and vegetables and simmer the sauce on the stovetop to reduce it.

Can this recipe be made without pearl onions?

Yes, you can substitute pearl onions with a large yellow onion, chopped into chunks. The flavor will be slightly different but still delicious. If using frozen pearl onions, there's no need to thaw them first; add them directly to the slow cooker.

Recipe card

Cowboy Butter Flank Steak Slow Cooker Dinner

Prep 10 minCook 6 hRest 10 minTotal 6 h 20 minServes 6

Ingredients

2 lb flank steak, thinly sliced against the grain
1 cup peeled pearl onions
2 cups crinkle-cut carrots
2 sticks garlic-herb cowboy butter (store-bought or homemade)
1 oz dry au jus mix

Instructions

Place the sliced flank steak strips in the bottom of a 6-quart slow cooker. Scatter the pearl onions and crinkle-cut carrots over the beef. Place the sticks of garlic-herb cowboy butter on top, then sprinkle the dry au jus mix evenly over everything. Do not stir.
Cover the slow cooker and cook on LOW for 6 to 7 hours, or on HIGH for 3 to 4 hours, until the beef is fork-tender and easily shreds. The butter will melt and combine with the au jus mix to create a rich, savory sauce. Let it rest for 3 minutes before slicing.
Turn off the slow cooker and let the beef rest in the sauce for at least 10 minutes. Use a slotted spoon to transfer the beef, onions, and carrots to a serving platter or over mashed potatoes. Spoon some of the au jus over the top before serving.

Contains: milk, gluten

Estimated nutrition per serving

Calories: 420
Protein: 34 g
Carbohydrates: 12 g
Fat: 26 g

Automatic estimate from the ingredient list, not laboratory-verified.

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This recipe is based on a short cooking video and is published under the pen name Clara Weller. It was checked before publication, but errors can slip through. Nutrition, when shown, is an estimate. Read more in our editorial policy and on our food safety page.