Cowboy Butter Broccoli Flank Steak: 5-Ingredient Crockpot Dinner

This Crockpot cowboy butter broccoli flank steak is the definition of set-it-and-forget-it cooking. Just layer flank steak strips, broccoli, mushrooms, garlic-herb butter, and au jus mix in the slow cooker, then walk away.

Hours later, you come back to a bubbling pot of fork-tender beef and vegetables in a rich, golden, buttery sauce. It's a complete dinner that tastes like you simmered it all day—because you did, but with almost zero effort. Serve it over creamy mashed potatoes for the ultimate comfort meal.

This recipe is built on a simple, genius method: dump everything into the slow cooker and let time do the work. The flank steak, sliced thin and cooked low and slow, becomes meltingly tender. The broccoli and mushrooms soften and soak up the savory au jus, while the garlic-herb butter melts into a luscious sauce that coats every bite.

It's a five-ingredient dinner that feels indulgent and tastes like a special occasion, yet requires just 10 minutes of prep. Perfect for busy weeknights or lazy Sundays, this dish is proof that the best meals are often the simplest.

Ingredients

Why this recipe works

The slow cooker's gentle, moist heat transforms a lean, tough cut like flank steak into fork-tender perfection. Cooking it low and slow breaks down the connective tissue without drying out the meat, leaving it succulent and easy to shred. The thin slices ensure even cooking and maximum surface area for the sauce to cling to.

The combination of garlic-herb butter and au jus mix creates a deeply savory, buttery sauce with almost no effort. As the butter melts, it emulsifies with the juices from the beef and vegetables, forming a rich, glossy gravy.

The broccoli and mushrooms cook in this flavorful liquid, absorbing all the goodness and becoming the perfect companions to the beef.

Notes and substitutions

Flank steak is the star here—look for a whole flank steak and slice it yourself against the grain into thin strips. If flank steak isn't available, sirloin or chuck roast work well, but adjust cooking times accordingly. Broccoli florets should be uniform in size so they cook evenly; frozen florets can be used, but reduce the cook time slightly.

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

Au jus gravy mix is typically found in the gravy or soup aisle; any brand works. For a gluten-free option, choose a gluten-free au jus mix and ensure the butter is dairy-free if needed.

• flank steak: sirloin steak or chuck roast, sliced thin; adjust cook time for chuck to 8 hours on low
• broccoli florets: broccolini or cauliflower florets (add in the last 30 minutes if you prefer crisp-tender)
• baby bella mushrooms: white button mushrooms or cremini mushrooms
• au jus gravy mix: 1 packet of brown gravy mix or 2 tablespoons of Worcestershire sauce plus 1 cup beef broth

Equipment

• 6-quart slow cooker
• Cutting board
• Chef's knife
• Measuring cups and spoons
• Serving spoon
• Serving plates