This Vegetarian Portobello Pot Roast recipe can be made easily in theย slow cooker or Instant Pot (pressure cooker). And it’s SO hearty and comforting and delicious!

As a Midwestern girl through and through, I’ve gotta admit, I will always love me a good pot roast. But hey, whoever said that had to includeย roastย beef?
A few weeks ago, when Iย found myself with two leftover cartons of baby bella mushrooms in the fridge that needed to be used up stat, I decided to try swapping them in as the main ingredient in my traditional pot roast recipe. And lo and behold, they turned out to be a plant-based swap made in heaven. This vegetarian pot roast recipe was a total winner!
It’s still full of those classic savory flavors (and garlicky gravy) that we all love. It’s quick and easy to prep, and easy to make either on the stovetop or in the slow cooker or Instant Pot. It’s naturally vegetarian and vegan. And it’s totally, wonderfully delicious.
My kind of comfort food.
To make the recipe, start by gathering lots of your starring ingredient — portobello mushrooms. You’re welcome to use full-size portobellos if you’d like. Or, you can be like me and just use a few cartons of baby bellas. Chop them up into bite-sized pieces…
…then combine them in a slow cooker or pressure cooker, along with some potatoes, carrots, pearl onions, garlic, and all of the ingredients for that classic savory gravy. Cook until the potatoes are nice and tender. Then for a final step, thicken that gravy up a notch…
…and voila! This deliciousย veggie-filled mushroom pot roast will be yours to serve and enjoy!
I went old-school and served mine over some egg noodles, but someย grains or rice would also work well here. I served mine up with this simple salad and some red wine, and the meal was perfection.
Vegetarian twist for the win!
Vegetarian Portobello Pot Roast
- Prep Time: 10 minutes
- Cook Time: 240 minutes
- Total Time: 250 minutes
- Yield: 6 -8 servings 1x
Description
This vegetarian Portobello Pot Roast recipe is quick and simpleย to prep, easy to cook in the Instant Pot or slow cooker, and it’s full of theย classic savory flavors we all love!
Ingredients
- 1.25 pounds Yukon gold potatoes, cut into bite-sized pieces
- 1 pound baby bella mushroomsย (if they are large, cut them in half)
- 2 large carrots, peeled and cut intoย bite-sized pieces
- 2 cups frozen pearl onions*
- 4 cloves garlic, peeled and minced
- 3 sprigs fresh thyme
- 3 cups vegetable stock, divided
- 1/2 cup dry red or white wine
- 3 tablespoons tomato paste
- 2 tablespoons vegetarian Worcestershire sauce*
- 2 tablespoons cornstarch
- Kosher salt and freshly-cracked black pepper
- optionalย garnish: finely-chopped fresh parsley
Instructions
Slow Cooker Method:
- Add potatoes, mushrooms, carrots, onions, garlic, thyme, 2.5 cups vegetable stock, wine, tomato paste and worcestershire together in the bowl of a crock pot, and gently toss to combine. ย Cook on low for 6-8 hours, or on high for 3-4 hours, until the potatoes and carrots are tender.
- In a separate bowl, whisk together the remaining 1/2 cup vegetable stock and cornstarch until combined. ย Add to the roast mixture, and gently toss to combine. ย Continue to cook for 1-3 minutes, until the sauce thickens up a bit.
- Serve immediately, garnished with fresh parsley if desired.
Instant Pot Method:
- Add potatoes, mushrooms, carrots, onions, garlic, thyme, 2.5 cups vegetable stock, wine, tomato paste and worcestershire together in the bowl of a pressure cooker, and gently toss to combine. ย Close lid securely and set vent to โSealingโ.
- Press โManualโ, then press โPressureโ until the light on โHigh Pressureโ lights up, then adjust the up/down arrows until time reads 20ย minutes. ย Cook. ย Then let the pressure release naturally, about 15 minutes. ย Carefully turn the vent to โVentingโ, just to release any extra pressure that might still be in there. ย Remove the lid.
- In a separate bowl, whisk together the remaining 1/2 cup vegetable stock and cornstarch until combined. ย Add to the roast mixture, and gently toss to combine. ย Continue to cook for 1-3 minutes, until the sauce thickens up a bit.
- Serve immediately, garnished with fresh parsley if desired.
Notes
Onions: Feel free to sub in sliced white onions, ifย pearl onions are not available.
Worcestershire: If making this recipe vegetarian, be sure to use vegan Worcestershire sauce.
***Cook time listed above is forย a slow cooker set on “high”.








I added only 2.25 cups stock in the beginning and still had to use 3 tbsp cornstarch to get it to thicken after cooking on high 4 hours. I would put less stock in and be ready to go over on the cornstarch. I added some italian seasonings as well, which worked with the overall flavor. Otherwise, quick and easy recipe.
Can the wine be skipped on this recipe?
I added 4 tbsp cornstarch and turned my instant pot to sautรฉ. When using cornstarch liquid needs to be simmering to slow boil for it to thicken. I also added a 1/2 tsp kitchen bouquet for a darker gravy. All in all, recipe is very good, serving over corn grits.
Sooo I love the idea and I am enjoying eating it but the instant pot timing is WAY too long. I reduced to 10 minutes and it was still too long. Next time Iโll do 5 minutes with quick release. I added some extra seasonings: 1t smoke paprika, 1 t garlic powder, 1 t ground thyme, 1 T tamari. Will make again!
It did need a bit more seasoning and it was thinner than I’d hoped, but otherwise it was great. After reading comments, I put my crockpot on low for 6 hrs but turned it off after about 5. Served over whole wheat pasta and even my toddler ate every bite!
This recipe was very good, but I would suggest changing the serving size. This would feed perhaps 3-4, but definitely not 6-8.
I cut the recipe in half and forgot to add the wine and the last step. Turned out beautifully in my new tiny 2 quart pressure cooker ๐