Cowboy Butter Pepper Sirloin Tips Slow Cooker Dinner

This slow cooker recipe delivers tender, juicy sirloin tips with sweet bell peppers and onions in a rich, buttery au jus. With just a few ingredients and a simple dump-and-go method, it’s the perfect weeknight dinner that tastes like you spent hours tending the stove.

The garlic-herb cowboy butter melts into a savory sauce that coats every bite, while the slow cooker does all the work. Serve over mashed potatoes or crusty bread to soak up every last drop.

These cowboy butter pepper sirloin tips are the ultimate set-it-and-forget-it dinner. Cubed sirloin steak tips are slow-cooked with colorful bell peppers and red onions, then topped with a generous amount of garlic-herb butter and a packet of au jus mix.

The result is fork-tender beef in a deeply savory, buttery sauce that’s perfect for spooning over mashed potatoes, rice, or noodles. This recipe comes together in minutes and delivers big, comforting flavor with minimal effort—ideal for busy evenings when you want a hearty meal without hovering over the stove.

Ingredients

Why this recipe works

Slow cooking is the secret to transforming a relatively lean cut like sirloin tips into fork-tender, melt-in-your-mouth bites. The low, steady heat breaks down the connective tissue while the beef simmers in its own juices and the seasoned butter, keeping it moist and succulent. The long cooking time also allows the flavors of the garlic, herbs, and au jus to permeate every piece of meat and vegetable, creating a cohesive, deeply savory dish.

The garlic-herb cowboy butter is the flavor powerhouse here. As it melts, it emulsifies with the beef juices and au jus to form a silky, rich sauce that clings to the meat and peppers.

The butter adds a luxurious mouthfeel and a hint of herbaceous brightness that balances the savory richness of the au jus. This simple technique—layering raw ingredients and letting the slow cooker work its magic—produces a complex, restaurant-quality meal with almost zero active cooking time.

Notes and substitutions

For the best results, buy steak tips that are already cut for stew or stir-fry, or cut a whole top sirloin roast into 2-inch pieces yourself. The even size ensures they cook at the same rate. If you prefer a leaner option, you can trim excess fat from the tips before cooking. The bell peppers and onion are sliced thick so they hold their shape during the long cook time, offering tender yet substantial bites.

Garlic-herb cowboy butter is a compound butter made with softened butter, minced garlic, fresh parsley, and sometimes a touch of Worcestershire or hot sauce.

You can find it pre-made in some grocery stores, or you can easily make your own by mixing 4 tablespoons softened butter with 2 minced garlic cloves and 1 teaspoon dried parsley. The au jus mix is typically found in the gravy section of the supermarket; choose a low-sodium version if you prefer to control the salt.

• top sirloin steak tips: chuck roast, cut into 2-inch cubes (cook longer, about 8 hours on low)
• garlic-herb cowboy butter: 4 tablespoons unsalted butter mixed with 2 minced garlic cloves and 1 teaspoon dried parsley
• au jus gravy mix: 1 tablespoon beef base mixed with 1 cup hot water
• green bell pepper: any color bell pepper or a poblano pepper for mild heat

Equipment

• Slow cooker (5-6 quart)
• Cutting board
• Chef's knife
• Measuring spoons
• Serving spoon
• Plate for serving