Dinner · Part 3 of 3: Tips & recipe card

Slow-Cooker Portobello Herb Garlic Butter Roast Tips, FAQ & printable recipe

Name: Slow-Cooker Portobello Herb Garlic Butter Roast
Prep time: 15 min
Cook time: 8 h
Total time: 8 h 25 min
Cuisine: American
Ingredients: 3 1/2 lb beef bottom round roast; 8 oz portobello mushroom caps, thickly sliced; 2 tbsp minced garlic; 4 medallions garlic-herb compound cowboy butter

By Clara Weller · Oct 28, 2026

Slow-cooker beef roast with mushrooms and gravy in a black crockpot

Prep: 15 min
Cook: 8 h
Total: 8 h 25 min
Serves: 6

Includes 10 min resting

Tips for success

For the most flavorful gravy, don't be shy with the garlic—two tablespoons is just the start. You can add a bit more if you love garlic.

Also, consider adding a splash of beef broth or red wine to the slow cooker if you want a thinner sauce, but the recipe works perfectly as-is. The butter and meat juices create plenty of liquid.

When shredding the beef, do it right in the slow cooker so the meat soaks up the gravy. Use two forks and pull in opposite directions for nice, long shreds.

If you prefer chunkier pieces, just break the meat into large chunks instead. Serve over noodles, mashed potatoes, or even polenta—the gravy is the star.

Variations

Red Wine Gravy: Add 1/2 cup dry red wine to the slow cooker before cooking. The wine adds depth and a slightly tangy note that pairs beautifully with the beef and mushrooms. Reduce the cooking time by 30 minutes if adding extra liquid.
Spicy Cowboy Butter: Mix 1/2 teaspoon smoked paprika and a pinch of cayenne into the cowboy butter before forming medallions. This adds a subtle smokiness and a gentle heat that complements the garlic and herbs.
Vegetable Add-In: Add 2 large carrots, cut into chunks, and 2 celery stalks, sliced, to the bottom of the slow cooker before adding the beef. This adds sweetness and texture, making it a more complete one-pot meal.
Herb Swap: If you don't have cowboy butter, use a mixture of softened butter, 1 teaspoon dried thyme, 1 teaspoon dried rosemary, and 2 cloves minced garlic. This herb blend infuses the meat with classic roast flavors.

Storage and make-ahead

Fridge: Store in an airtight container in the fridge for up to 4 days. Reheat gently on the stovetop or microwave, adding a splash of broth if needed.
Freezer: Freeze in a freezer-safe container for up to 3 months. Thaw overnight in the fridge before reheating.
Reheat: Reheat in a saucepan over medium-low heat, stirring occasionally, until hot and bubbly. For single servings, microwave in 30-second bursts, stirring in between.

Store leftover shredded beef and gravy in an airtight container in the refrigerator for up to 4 days. The flavors will continue to meld, making it even more delicious. Reheat gently on the stovetop or in the microwave, adding a splash of water or broth if the gravy has thickened too much.

This recipe is ideal for making ahead. You can assemble the raw ingredients in the slow cooker insert the night before, cover, and refrigerate.

In the morning, place the insert in the slow cooker and cook as directed. The beef and gravy also freeze beautifully, so you can make a double batch and save half for later.

Serving ideas

Serve this slow-cooker roast over warm buttered egg noodles for a classic, comforting meal. The noodles soak up the rich gravy, making every bite satisfying.

A side of crusty bread is perfect for sopping up any extra sauce. For a lighter option, serve over mashed cauliflower or roasted vegetables.

Garnish with fresh chopped parsley or chives for a pop of color and a hint of freshness. The dish is hearty enough to stand alone, but a simple green salad with a tangy vinaigrette would balance the richness nicely. Leftovers are even better the next day, so don't be afraid to make extra.

Frequently asked questions

Can this roast be made on high instead of low?

Yes, the roast can be cooked on high for 4 to 5 hours instead of low for 8 to 10 hours. The texture will be slightly less tender, but still delicious. Always check for fork-tenderness before serving.

What can be used instead of portobello mushrooms?

Cremini or white button mushrooms work well as substitutes. Use about 8 ounces and slice them thick. They will have a slightly milder flavor but will still contribute a meaty texture to the dish.

Can the beef be seared before adding to the slow cooker?

Yes, searing the roast in a hot skillet with a little oil before adding it to the slow cooker adds extra flavor and color. It's not necessary, but it can enhance the overall depth of the dish.

Is it necessary to add liquid to the slow cooker?

No, the beef and mushrooms release enough liquid during cooking, and the butter melts into a rich sauce. Adding extra liquid can make the gravy too thin. If the roast looks dry, add a splash of beef broth.

How can the gravy be thickened if it's too thin?

If the gravy is too thin after shredding, mix 1 tablespoon cornstarch with 2 tablespoons cold water and stir into the hot gravy. Cook for a few minutes until thickened. Alternatively, mash some of the mushrooms to thicken naturally.

Recipe card

Slow-Cooker Portobello Herb Garlic Butter Roast

Prep 15 minCook 8 hRest 10 minTotal 8 h 25 minServes 6

Ingredients

3 1/2 lb beef bottom round roast
8 oz portobello mushroom caps, thickly sliced
2 tbsp minced garlic
4 medallions garlic-herb compound cowboy butter

Instructions

Place the beef bottom round roast in the center of the slow cooker insert. It's okay if it fits snugly; the meat will shrink as it cooks. No need to sear—the slow cooker does the work.
Scatter the sliced portobello caps over and around the roast. Sprinkle the minced garlic evenly over the mushrooms and meat. The garlic will infuse the gravy as it cooks.
Place the medallions of cowboy butter on top of the roast. As the butter melts, it will create a rich, herby gravy that bastes the meat and mushrooms.
Cover the slow cooker and cook on low for 8 to 10 hours, or on high for 4 to 5 hours, until the beef is fork-tender and easily shreds. The internal temperature should reach at least 145°F (63°C), but for braising, it will go higher. Let it rest for 3 minutes before slicing.
Once the beef is tender, turn off the slow cooker. Let the roast rest in the liquid for at least 10 minutes. This allows the juices to redistribute and makes shredding easier.
Using two forks, shred the roast directly in the slow cooker. Stir the shredded beef into the gravy so every piece is coated. The mushrooms will have softened and blended into the sauce.
Spoon the shredded beef and mushroom gravy over warm buttered egg noodles or your favorite side. The gravy will soak into the noodles, making every bite rich and savory.

Contains: milk

Estimated nutrition per serving

Calories: 450
Protein: 35 g
Carbohydrates: 6 g
Fat: 30 g

Automatic estimate from the ingredient list, not laboratory-verified.

Next recipe

Fork-tender beef roast with portobello mushrooms in a buttery jus in a slow cooker

Dinner · 8 h 15 min

Crockpot Portobello Butter Bottom Round Roast

See the recipe → →

This recipe is based on a short cooking video and is published under the pen name Clara Weller. It was checked before publication, but errors can slip through. Nutrition, when shown, is an estimate. Read more in our editorial policy and on our food safety page.