Cowboy Butter Portobello Tenderloin Tips: Slow-Cooker Dinner

This slow-cooker dinner brings together tender beef tenderloin tips, meaty portobello mushrooms, and sweet shallots in a rich, garlic-herb butter au jus. The ingredients go into the Crockpot in minutes, then the slow cooker does all the work, filling the kitchen with an irresistible aroma. Serve the saucy beef over mashed potatoes for a satisfying weeknight meal that feels special but requires almost no effort.

Beef tenderloin tips are already a tender cut, but simmering them low and slow with butter and au jus takes them to another level. The portobello mushrooms soak up the savory sauce, while the shallots turn sweet and silky.

This recipe is a true dump-and-go dinner: just layer the ingredients, set the slow cooker, and come back to a bubbling pot of rich, beefy goodness. It’s perfect for busy days when you want a hearty, homemade meal without standing over the stove.

Ingredients

Why this recipe works

The slow cooker’s gentle, moist heat breaks down the connective tissue in the beef tenderloin tips, making them exceptionally tender without drying out. The butter and au jus create a rich, savory sauce that coats every bite, while the mushrooms and shallots absorb the flavors and add their own depth.

This hands-off method allows the ingredients to meld together slowly, developing a complex, comforting taste that tastes like it simmered all day—because it did.

Cooking the beef on low for an extended period is forgiving, so there’s no need to watch the pot. The fat from the butter and the natural juices from the beef keep everything moist, and the au jus mix provides a concentrated beefy flavor. This method is ideal for busy cooks: it requires minimal prep, uses common ingredients, and yields a dish that tastes rich and homemade with almost no effort.

Notes and substitutions

Beef tenderloin tips are typically sold already trimmed and cut, but you can also buy a whole tenderloin and cut it into 1-inch pieces yourself. If you can’t find tenderloin tips, sirloin steak cut into cubes works well, though it may need slightly less cooking time.

Portobello mushrooms should be thickly sliced so they hold their texture during the long cook. Shallots can be replaced with a small yellow onion cut into wedges if needed.

Garlic-herb cowboy butter is a compound butter with garlic, herbs, and often a hint of spice. You can use store-bought or make your own by mixing softened butter with minced garlic, chopped parsley, thyme, and a pinch of cayenne.

If you don’t have cowboy butter, use unsalted butter mixed with garlic and dried herbs. The dry au jus mix is essential for the savory sauce; if you prefer, use a beef broth-based seasoning mix.

• beef tenderloin tips: sirloin steak, cut into 1-inch cubes (cook time may need to be reduced slightly)
• portobello mushrooms: cremini or white button mushrooms, thickly sliced
• shallots: 1 small yellow onion, cut into wedges
• garlic-herb cowboy butter: 1/2 cup (1 stick) unsalted butter mixed with 2 minced garlic cloves and 1 teaspoon dried herbs (such as thyme and rosemary)

Equipment

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