Cowboy Butter Flank Steak Slow Cooker Dinner

This slow cooker flank steak recipe is the ultimate set-it-and-forget-it dinner. Thin strips of flank steak cook low and slow with sweet pearl onions and carrots in a rich, savory garlic-herb butter au jus.

The result is fork-tender beef that melts in your mouth, with a sauce that's perfect for spooning over mashed potatoes or crusty bread. It's a comforting, hearty meal that comes together with just a few minutes of prep.

Flank steak is a lean, flavorful cut that benefits from long, slow cooking to become tender. In this recipe, it's sliced thin and layered in the slow cooker with pearl onions and carrots, then topped with garlic-herb cowboy butter and a packet of au jus mix.

The butter melts into a luscious sauce that infuses the beef and vegetables with rich, savory flavor. This is a hands-off dinner that delivers big on taste with minimal effort.

Ingredients

Why this recipe works

The slow cooker provides a moist, gentle heat that breaks down the connective tissue in flank steak, turning a tough cut into buttery-soft morsels. Cooking on low for several hours allows the beef to become fork-tender without drying out, while the pearl onions and carrots soften and absorb the savory sauce.

The combination of garlic-herb cowboy butter and au jus mix creates a deeply flavorful cooking liquid. The butter adds richness and a silky mouthfeel, while the au jus mix provides a savory, beefy backbone.

As the beef simmers, the flavors meld and concentrate, resulting in a sauce that tastes like it simmered all day.

Notes and substitutions

For the best texture, slice the flank steak against the grain into thin strips. This shortens the muscle fibers, making each bite more tender. If you prefer larger chunks, you can cut the steak into 2-inch pieces, but thin strips cook faster and are easier to serve.

Garlic-herb cowboy butter is a flavored butter with garlic, herbs, and often a hint of spice. You can find it in the dairy section of many supermarkets, or make your own by mixing softened butter with minced garlic, parsley, chives, and a pinch of cayenne.

If you don't have cowboy butter, use regular butter and add extra herbs and garlic to the slow cooker.

• flank steak: sirloin steak or chuck roast, sliced thin
• pearl onions: frozen pearl onions, thawed, or 1 large yellow onion, chopped
• crinkle-cut carrots: baby carrots or sliced regular carrots
• garlic-herb cowboy butter: 4 tbsp unsalted butter mixed with 1 tsp garlic powder and 1 tsp dried herbs

Equipment

• 6-quart slow cooker
• Cutting board
• Sharp knife
• Measuring cups
• Measuring spoons
• Serving spoon
• Dinner plates