Cowboy Butter Mushroom Flank Steak Crockpot Dinner

This Crockpot Cowboy Butter Mushroom Flank Steak is the definition of set-it-and-forget-it comfort food. Tender strips of flank steak slow-cook in a rich, savory sauce made with cream of mushroom soup, garlic-herb cowboy butter, and au jus.

The result is a deeply flavorful, melt-in-your-mouth beef dinner that tastes like it simmered all day—because it did. Serve it over whipped mashed potatoes for a complete, satisfying meal that will become a weeknight favorite.

There are dinners that require effort, and then there are dinners that require almost none—yet deliver incredible flavor. This Crockpot flank steak is the latter. You simply layer the ingredients in the slow cooker, walk away, and return hours later to a bubbling pot of fork-tender beef and mushrooms in a luscious garlic-herb gravy.

The combination of condensed mushroom soup, cowboy butter, and au jus creates a sauce that's rich, savory, and deeply satisfying. Perfect for busy evenings when you want a home-cooked meal without the fuss.

Ingredients

Why this recipe works

Slow cooking is the secret to transforming an affordable cut like flank steak into a fork-tender, succulent main. The low, gentle heat breaks down the connective tissue in the meat, resulting in strips that are juicy and tender, not tough or chewy. The long cooking time also allows the flavors of the butter, soup, and au jus to meld and penetrate the beef, creating a deeply savory sauce.

The method is deliberately hands-off: no searing, no stirring, no babysitting. Layering the ingredients in the order specified ensures that the beef stays moist and the seasonings distribute evenly.

The cream of mushroom soup acts as a thickener, while the cowboy butter adds richness and aromatic herbs. The au jus mix provides a savory, beefy backbone that ties everything together. This is a true dump-and-go recipe that rewards you with a hearty, restaurant-quality meal.

Notes and substitutions

Flank steak is the star here, but you can also use sirloin or round steak—just slice it thinly against the grain. The cream of mushroom soup is a classic shortcut that adds creaminess and umami; if you prefer, use cream of chicken or a homemade condensed mushroom sauce.

The garlic-herb cowboy butter is available in many grocery stores, but you can make your own by mixing softened butter with minced garlic, parsley, chives, and a pinch of paprika.

The dry au jus mix is essential for that deep, beefy flavor. Look for it in the gravy or soup aisle. If you can't find it, substitute beef bouillon granules plus a little onion powder. The mushrooms are optional but highly recommended—they soak up the sauce and add earthy texture. For the best results, use a 6- to 7-quart slow cooker to ensure even cooking and prevent overflow.

• flank steak: sirloin steak or round steak, thinly sliced
• cream of mushroom soup: cream of chicken soup or a homemade condensed mushroom sauce
• garlic-herb cowboy butter: regular butter mixed with 2 minced garlic cloves and 1 teaspoon dried herbs
• au jus mix: 1 tablespoon beef bouillon granules plus 1/2 teaspoon onion powder

Equipment

• 6- to 7-quart slow cooker
• Cutting board
• Chef's knife
• Measuring spoons
• Serving spoon
• Dinner plates