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Home » Recipes » Crockpot Recipes

Portobello Mushroom Sandwich

Published: Aug 7, 2022 · Modified: Aug 18, 2022 by Debra Clark · 28 Comments

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Do you love a great sloppy-joe but want to lighten up your meal? This Portobello Mushroom Sandwich  is the easiest and most delicious sandwich.

Cooked in the slow cooker or Instant Pot (works for either!) It takes ten minutes in prep and it's hands off after that.

Next time try Sautéed Portobello Mushrooms!

Close-up picture of a sandwich. The bottom bun is topped with lettuce, portobello mushroom, red peppers and onions. The sandwich is topped with crunchy coleslaw and finished off with a big bun on top.
No one will miss the meat with this big meaty Portobello Mushroom Sandwich!
Jump to:
  • Why you'll love this recipe
  • Ingredients
  • Instructions
  • FAQ's
  • Tips
  • Things to know
  • Related recipes
  • Serve with
  • Portobello Mushroom Sandwich
  • Recipe backstory

Why you'll love this recipe

✔️ Great vegetarian meal, you won't miss the meat!

✔️ Loaded with flavor, it's easy to make and delicious.

✔️ 10 minutes of prep time!

And I might add...I've came pretty close (Dan says it's better!) ! This burger is slow cooked with mushrooms, red onions and bell peppers. I

Ingredients

Mushroom Burger on plate.
Portobello Mushroom Sandwich
A burger bun topped with lettuce, portobello mushroom, onions and peppers. There's a spoonful of coleslaw being placed on the top.
Top each sandwich with a dollop of coleslaw.

For the exact measurements, please refer to the printable recipe card at the bottom of this post. 

  • portobello Mushrooms
  • sliced Mushrooms
  • red onion
  • red bell pepper
  • bbq sauce
  • fixings for coleslaw (or pre-made from the Deli department)

Instructions

Collage of photos showing steps to make recipe.
Here are the steps!

This is an overview of the instructions. For the complete directions just scroll down to the bottom!

  1. clean the mushrooms, put them in the slow cooker
  2. add the sliced peppers and onions
  3. top with bbq sauce and spice. Stir to combine.
  4. toast the burger buns because this is an oozy-gooey burger and toasting the bun keeps it from getting soggy.
  5. Assemble the portobello mushroom sandwich, topping each with homemade slaw.

FAQ's

Are you supposed to eat the gills of a portobello mushroom?

You can eat the gills, but they can be tough and not very palatable. Scrape them out and discard.

Should you remove the stem?

Similar to the gills, the stem can be tough. Remove it and discard.

Is a mushroom a carb or protein?

Mushroom are very low carb and have a little protein.

A burger bun topped with portobello mushroom, onions and peppers in barbecue sauce.
When you plate the Portobello Mushroom Sandwich, position the mushroom stem side up. It creates a bowl to hold the sliced mushrooms, peppers and onions.

Tips

This meal can be made in the slow cooker or Instant Pot. While it is cooking make the coleslaw and toast your burger buns. That's it!

Use homemade bbq sauce or store bought sauce, either works!

Portobello mushroom sandwich on plate.

When you assemble the burger, place the portobello on the bun first stem side up. Placing it with the stem side up creates a natural bowl for the sliced mushrooms, peppers and onions and keeps them from sliding off - then top it off with a big dollop of cole slaw!

Portobello mushrooms give the sandwich that big steak flavor and making it in your slow cooker is super easy. A Portobello Mushroom Sandwich is big, meaty, hearty and most of all delicious!

Things to know

Sandwich on plate.
  • toast or grill the bread (keeps it from getting soggy)
  • remove the gills from the portobello mushrooms
  • place the portobello mushroom on the bun first, stem side up - this creates a natural bowl for the sliced mushrooms, peppers and onion
  • can be made in the instant pot

Related recipes

There are several great sandwiches on the blog - here are some of the favorites!

  • Peanut Butter Honey Sandwich - a classic family favorite!
  • Tomato Sandwich with Avocado and Pesto - perfect in the summertime when you're looking for a light meal.
  • Avocado Toast Breakfast Sandwich - this is so good and a great way to start the day.

Read about more of our adventures here - Family Fun Night with the Oakland A's and our visit to Mesa Verde National Park

Serve with

  • Salad and sandwich is always delicious - serve with Mom's Deviled Egg Potato Salad Recipe or a great Green Salad with Fruit.
  • Top your sandwich with some yummy Tomato Relish!
  • This recipe for Mexican fruit salad is another great pairing.

Don't forget to check out my Amazon storefront for some of my favorite products! 🛍️

If you love this recipe please leave a ⭐⭐⭐⭐⭐ rating! 

Portobello Mushroom Sandwich on plate.
4.86 from 7 votes

Portobello Mushroom Sandwich

This Portobello Mushroom Sandwich is the BEST! Big, rich and meaty this vegetarian burger will make you a believer of a meatless meal! It can be made in the slow cooker or Instant Pot and it's super easy.
Print Recipe Pin Recipe SaveSaved!
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Prep Time15 minutes mins
Cook Time4 hours hrs
Total Time4 hours hrs 15 minutes mins
Course: Vegetarian
Cuisine: American
Servings: 2 sandwiches
Calories: 712kcal
Author: Deb Clark

Ingredients

  • 2 portobello mushrooms
  • 1 16 oz package pre-sliced mushroom
  • 1 red bell pepper
  • ½ red onion
  • ½ cup bbq sauce - use your favorite
  • 1 teaspoon salt
  • ½ teaspoon pepper
  • healthy pinch red pepper flakes
  • Coleslaw
  • ½ head cabbage
  • 2 carrots
  • ½ red onion
  • ½ cup mayonnaise
  • 2 tablespoons cider vinegar
  • 2 tablespoons honey
  • salt and pepper to taste

Instructions

  • Clean the portobello mushrooms, remove the stem & fins, place in the slow cooker. Top with the pre-sliced mushrooms.
  • Slice the bell pepper, remove the seeds and slice into strips. Remove the outer peel from the onion and slice into strips. Place into the slow cooker with the mushrooms.
  • Season the vegetables with salt, pepper & red pepper flakes, top with bbq sauce. Put the lid on the slow cooker & cook on high for 4 hours or low for 6.
  • While the meal is cooking, make the cole slow. Thinly slice the cabbage, clean & shred the carrots (I use a box grater.), thinly slice the onions, place in a large bowl.
  • Mix the coleslaw dressing together - it will be quite thick, but that's how you want it. Mix the dressing with the vegetables, refrigerate until ready to use.
  • Toast the burger buns.
  • Assemble and enjoy!

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    Nutrition

    Calories: 712kcal | Carbohydrates: 78g | Protein: 7g | Fat: 43g | Saturated Fat: 6g | Cholesterol: 23mg | Sodium: 2349mg | Potassium: 1258mg | Fiber: 11g | Sugar: 59g | Vitamin A: 12475IU | Vitamin C: 167.1mg | Calcium: 147mg | Iron: 2.3mg

    Recipe backstory

    Miles of gorgeous beach. We usually have the beach to ourselves! Absolutely breathtaking beauty!

    In the city of Waimanalo there is a tiny little five star vegan restaurant. Here we discovered the most amazing food! 'Ai Love Nalo keeps sparse hours and always has a line out the door.

    The food is spectacular! This blog was first released two years ago. Since then every time we visit Hawaii, we dine at this restaurant.

    We enjoyed a couple of meals there and a favorite is the Mushroom Burger - hands down the most fantastic burger (beef, chicken or vegan) that I've ever eaten. I've done my best since we came home to replicate that burger!

    This vegetarian meal was inspired by our visit to Hawaii a couple years ago. This is a blog I released two years ago. As I was updating the recipe and pictures, I realized many of the pictures are worth sharing again, so enjoy!

    I did promise you a recipe today and that recipe is for a delicious Portobello Mushroom Sandwich. This sandwich was inspired by our visit to Hawaii. When we are there, we often stay in Waimanalo which is on the eastern side of Oahu. It's the most picturesque beach I've ever seen.

    Now that burger we had at 'Ai Love Nalo was pretty fabulous and I have to say, I've worked to make this recipe comparable and my hubby say I nailed it!

    More Crockpot Recipes

    • Forkful of cheesy green chile chicken enchilada casserole being lifted from a crockpot, topped with diced tomatoes and green peppers.
      Crockpot Green Chile Chicken Enchiladas
    • Plated slow cooker corn on the cob sprinkled with black pepper and parmesan cheese.
      Slow Cooker Corn on the Cob
    • Melted cheese stretching from a spoonful of French onion chicken fresh from the slow cooker.
      Crockpot French Onion Chicken
    • Slow Cooker Asparagus on a platter topped with melted cheese and garnished with lemon slices.
      Slow Cooker Asparagus

    About Debra Clark

    Hey I'm Deb Clark, and I'm the owner of Bowl Me Over! We live in the sleepy little town of Scappoose, Oregon. And I admit it... I love food! Join me in this foodie journey (even if you've never cooked before!) I will help you learn to be confident in the kitchen! Want to learn more? Let's stay connected, you can email me at debra@bowl-me-over.com and find me on Facebook, Pinterest, Instagram, Twitter and YouTube.

    Comments

      4.86 from 7 votes

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      Recipe Rating




    1. Lois says

      January 08, 2018 at 4:31 pm

      5 stars
      This looks like a very enjoyable sandwich that I will be enjoying this coming week. Love everything in them.

      Reply
      • Bowl Me Over says

        January 08, 2018 at 8:32 pm

        You would completely love this Mom. You're as big a fan of mushrooms as I am! 😀

        Reply
      • Mary Decker says

        December 27, 2021 at 7:57 am

        5 stars
        This looks very delicious! Can you tell me, Please, how you would adjust the recipe to see an Instant Pot? Thank you!

        Reply
        • Bowl Me Over says

          December 27, 2021 at 8:09 am

          Hey Mary - I've never used the pressure cooker for this recipe, however if I did, this is what I'd do - I'd sauté the peppers onions and sliced mushrooms in a tablespoon of oil first. Seasoning with salt, pepper and red pepper flakes. Then add the portobello mushrooms. Pour in half cup water. Increase the bbq sauce to one cup. Add the lid, seal. and set on manual. Set timer for four minutes and natural pressure release at the end. My only concern is the amount of liquid, so with that adjustment you should be set. Plus while it's cooking you can make the slaw. Enjoy! This is a delicious meal!!

          Reply
    2. Sandi says

      November 28, 2017 at 9:07 am

      5 stars
      I love that you made something delicious based on your family's vacation memory. The baby is just precious...and that burger, OMG yummy!

      Reply
      • Bowl Me Over says

        November 30, 2017 at 2:45 pm

        Thank you so much Sandi! Truly that's one of my favorite restaurants, we always dine there when we visit the Islands. And baby Juna... she has my heart! <3

        Reply
    3. Angela Campos says

      July 23, 2016 at 9:12 am

      These sound amazing! I LOVE anything I can make in the crockpot, Pinned 🙂

      Reply
      • Bowl Me Over says

        July 27, 2016 at 11:33 am

        With all humbleness....it's a terrific burger! 😀 I hope you give it a try!

        Reply
    4. Manju | Cooking Curries says

      July 18, 2016 at 12:43 am

      4 stars
      Such an adorable little baby girl!! The burgers look delicious. Bet you had a fabulous time over there!

      Reply
      • Bowl Me Over says

        July 18, 2016 at 1:37 pm

        Yes, yes and yes! 😀 Thanks Manju, I appreciate you stopping by!

        Reply
    5. Ilka says

      July 17, 2016 at 12:47 pm

      Debra - thanks for introducing us to your beautiful granddaughter Juna! I can see what a proud grandparents you are !
      The beach looks absolutely stunning and your recipe is fab as usual. Thanks for sharing this happy post with us. Pinning and stumbling! Congratulations!

      Reply
      • Bowl Me Over says

        July 18, 2016 at 1:41 pm

        Thank you so much Ilka and thanks for stopping by for sharing!

        Reply
    6. Janet Vinyard says

      July 17, 2016 at 8:25 am

      Hi Debra, Congratulations on your beautiful granddaughter! Thanks for sharing the recipe for Mushroom Burgers - I'm always looking for some meatless meals and this sounds great! Blessings, Janet

      Reply
      • Bowl Me Over says

        July 18, 2016 at 1:42 pm

        Thanks Janet! She is quite the little cutie 😀 but of course I am a bit biased, LOL! Enjoy that burger!

        Reply
    7. linda spiker says

      July 16, 2016 at 7:16 am

      5 stars
      Fabulous burger! Adorable baby!

      Reply
      • Bowl Me Over says

        July 18, 2016 at 1:48 pm

        Thank you Linda!

        Reply
    8. Nettie Moore says

      July 14, 2016 at 9:05 am

      Your slow cooker mushroom burger looks amazing!! Nettie

      Reply
      • Bowl Me Over says

        July 14, 2016 at 6:30 pm

        Thank you Nettie!!!

        Reply
    9. Michaela Kenkel says

      July 14, 2016 at 7:31 am

      First off -- CONGRATULATIONS on your sweet little one! You make being a grandma look so much fun! Beautiful pictures of her and of that incredible mushroom burger! SWOON! Makes me want to load up in the car and go grab the ingredients right now!

      Reply
      • Bowl Me Over says

        July 14, 2016 at 6:32 pm

        She is such a sweetie, thank Michaela!! And that burger...go...run now and grab those ingredients! 😀

        Reply
    10. christine says

      July 14, 2016 at 5:20 am

      Wow,, what a different burger. Love the flavors and super love that it's a slow cooker recipe. I want to pay more attention to it, but I just can't keep my eyes off that cutie pie baby! Oh what a love! And how stinkin cute is that little Hawaiian outfit? Seriously can't handle the cuteness!

      Reply
      • Bowl Me Over says

        July 14, 2016 at 6:35 pm

        Hahaha, love that little hula skirt, LOL!!! She is our little sweetie pie! The burger is kinda of a side note huh? 😀

        Reply
    11. Patty Haxton Anderson says

      July 14, 2016 at 4:47 am

      Seeing your kids and your grandchild - wow what a nice visit. See your hubby is your #1 supporter too! That burger, I would have never guessed it was done in a slow cooker. Holy cow it looks scrumptious. And, it's fun re-creating your restaurant favorites at home. Looks like you did it really well!

      Reply
      • Bowl Me Over says

        July 14, 2016 at 6:37 pm

        Thank you Patty it was a super great visit. The kids are so lucky to live in Hawaii, and we are lucky to be able to visit! 😀

        Reply
    12. Kelli says

      July 11, 2016 at 2:00 pm

      5 stars
      I love your pictures and i just bet Mom & Dad did also!!!!
      This burger looks fab, but alas i am gluten free so no bun....
      How about some Gluten-Free recipes????? Pretty Pls..
      thanks for all you do!! and for all you share!!
      God Bless

      Reply
      • Bowl Me Over says

        July 12, 2016 at 11:55 am

        Yes they did Kelli & thank you very much! Proud G&G here!!! 😀 Stay tune for GF - yours is not the first request I've received lately, thank you so much for letting me know what you're interested in! Thank you Kelli, be in touch again soon! 😀

        Reply
    13. Healing Tomato says

      July 11, 2016 at 1:55 pm

      5 stars
      Baby Juna is the most adorable baby! Hawaii is a such a beautiful place, isn't it? Nothing tastes quite as good as a mushroom burger. They make for a great base for a patty. The coleslaw adds a nice crunch. I have to make this recipe over the weekend.

      Reply
      • Bowl Me Over says

        July 12, 2016 at 11:53 am

        Thank you Rini - she is the sweetest baby!!! Enjoy that burger, it's our very favorite!

        Reply
    Blogger Deb Clark smiling at camera holding a plate filled with a casserole.
    Welcome to Bowl Me Over!

    Hey I'm Deb Clark! I'm the owner of Bowl Me Over. We live in a sleepy little town just north of Portland in the beautiful Pacific Northwest... (read more)

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