Cowboy Butter Mushroom Flank Steak Crockpot Dinner Tips, FAQ & printable recipe

Tips for success

For the most flavorful results, use a good-quality garlic-herb butter. If you can't find cowboy butter, make your own by mixing 1 cup softened butter with 2 minced garlic cloves, 1 tablespoon chopped parsley, 1 teaspoon dried thyme, and 1/2 teaspoon smoked paprika.

Let it firm up in the fridge before slicing. This homemade version adds a fresh, vibrant herb note that elevates the whole dish.

To thicken the sauce at the end, remove the beef and mushrooms with a slotted spoon, then simmer the sauce on HIGH for 15 to 20 minutes until it reduces.

You can also whisk in a slurry of 1 tablespoon cornstarch and 2 tablespoons cold water. This is especially useful if you prefer a thicker gravy for spooning over mashed potatoes.

Variations

• Add Bacon: Cook 4 slices of bacon until crisp, crumble, and stir into the sauce during the last 30 minutes of cooking. The smoky flavor pairs beautifully with the beef and mushrooms.
• Spicy Kick: Add 1/2 teaspoon of red pepper flakes or a diced jalapeño along with the onions. For extra heat, serve with a drizzle of hot sauce at the table.
• Vegetable Boost: Add 2 cups of baby carrots and 2 stalks of sliced celery with the onions. They will soften and absorb the sauce, adding sweetness and texture.
• Herb Swap: If you don't have cowboy butter, use 1/2 cup of regular butter plus 2 teaspoons of Italian seasoning. Add the butter at the start, and the herbs will infuse the sauce as it cooks.

Storage and make-ahead

Fridge

Store in an airtight container for up to 4 days. Reheat gently, adding a splash of broth if needed.

Freezer

Freeze in a freezer-safe container for up to 3 months. Thaw overnight in the refrigerator before reheating.

Reheat

Reheat in a saucepan over medium-low heat, stirring occasionally, until hot. Add a little beef broth or water if the sauce is too thick.

Leftovers can be stored in an airtight container in the refrigerator for up to 4 days. The flavors will continue to meld, making the leftovers even more delicious. Reheat gently on the stovetop or in the microwave, adding a splash of beef broth if the sauce has thickened too much.

This recipe is ideal for meal prep. Assemble the ingredients in the slow cooker insert the night before, cover, and refrigerate. In the morning, place the insert in the slow cooker and cook as directed.

You can also cook the full recipe, then freeze portions for up to 3 months. Thaw overnight in the refrigerator before reheating.

Serving ideas

Serve the cowboy butter mushroom flank steak over a generous scoop of whipped mashed potatoes. The creamy potatoes are the perfect foil for the rich, savory gravy.

For a complete meal, add a side of steamed green beans or a crisp green salad with a simple vinaigrette to cut through the richness.

This dish also works beautifully over egg noodles, rice, or polenta. If you're feeling indulgent, top each serving with a sprinkle of fresh parsley or chives. The leftovers are fantastic in a sandwich—pile the beef and gravy onto a toasted roll for a hearty lunch the next day.

Frequently asked questions

Recipe card

Cowboy Butter Mushroom Flank Steak Crockpot Dinner

Prep 10 minCook 6 hRest 5 minTotal 6 h 15 minServes 6

Ingredients

• 2 lb flank steak, thinly sliced against the grain
• 1 can (10.5 oz) condensed cream of mushroom soup
• 1 medium diced white onion
• 2 sticks (1/2 cup each) garlic-herb cowboy butter, sliced
• 1 oz dry au jus mix
• 8 oz sliced mushrooms
• Whipped mashed potatoes, for serving

Instructions

1. Place the sliced flank steak strips in the bottom of a 6- to 7-quart slow cooker. Spread the diced onion over the beef. Pour the condensed cream of mushroom soup over the top, using a spatula to spread it evenly. Add the sliced mushrooms if using.
2. Dot the garlic-herb cowboy butter over the top of the soup mixture. Sprinkle the dry au jus mix evenly over everything. Do not stir.
3. Cover the slow cooker and cook on LOW for 6 to 8 hours, or on HIGH for 3 to 4 hours, until the beef is fork-tender and easily shreds. Avoid opening the lid during cooking to keep the heat steady. Let it rest for 3 minutes before slicing.
4. Turn off the slow cooker and let the beef rest in the sauce for at least 5 minutes. This allows the juices to redistribute, keeping the meat moist.
5. Spoon the beef, mushrooms, and gravy over a bed of whipped mashed potatoes on each plate. Serve hot, with extra gravy spooned over the top.

Contains: gluten, milk, soy

Estimated nutrition per serving

Calories

420

Protein

32 g

Carbohydrates

12 g

Fat

26 g

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