These easy vegan portobello steaks topped with avocado are out of this world. Featuring juicy meaty textures, tons of flavors and creamy avocado they are everything summer (and every other season) is about. Make them on the grill, in the oven, or in a frying pan, and eat topped with soft Caramelized onions, in a burger, with a side of fries or mashed potatoes, and a salad. It’s a flavor bomb waiting to happen.
Jump to RecipeThese easy vegan portobello avocado-loaded steaks are ready to be the star of your summer…and not just for vegans and vegetarians. Think juicy meaty textures, tender flavor-packed mushrooms topped generously with creamy avocados, rich red pesto, sun-dried tomatoes, and soft Caramelized onions. It’s a plateful of deliciousness.
There’s nothing quite like that first bite of tender meaty mushrooms loaded with umami flavors and topped with red pesto that tastes like sunshine…not to mention the cool creaminess of the avocado that becomes zingy and earthy when it’s heated. It’s a true vegan steak that will satisfy even devout meat lovers.
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Today’s ingredient list is short and fabulously flavorful. Let’s dive right into what you need to make (and get at the grocery store) to make these tasty plant-based steaks.
- olive oil (you probably already have this in your kitchen)
- portobello mushrooms
- red pesto (homemade or store-bought)
- avocados, mashed with a fork
- oil-packed sun-dried tomatoes, chopped
- oregano (can be fresh or dried)
- salt
- pepper

But we can’t forget about the AMAZING soft Caramelized onions. I can describe these soft onions in one word only; “yum”.
They are decadent, and rich, and add to that real steak feeling. You can’t miss out on this portobello onion combo.
Making soft Caramelized onions is easy. Like, super easy. But it’s one of those extras that will take your vegan steak from great to absolutely delicious. And it requires barely any ingredients.

Let’s look at what you need to make Caramelized onions:
- olive oil
- yellow onions, sliced
- salt
- pepper
How to make Caramelized onions step-by-step
Heat olive oil in a pan. Once the pan is hot gently transfer the sliced onions to the pan and stir. Season with salt and pepper and let the onions cook at medium-high heat while stirring occasionally. The onions should cook for 15-minutes or until they are soft, Caramelized in places, and tender. Add extra salt if needed before serving.
Now, let’s take a look at the star of the show. These plant-based mushroom steaks are out of this world…and surprisingly simple to make. Whether you’re making them on the grill or in the oven it’s so simple.


How to Make portobello avocado steaks in the oven.
- Preheat the oven to 400F.
- Clean the portobello mushrooms and place them with the stem side up in a baking pan.
- Use a spoon or butter knife to spread a generous layer of red pesto on top of the mushrooms. Cut the avocados in half and carefully remove the stones without cutting yourself. Use a spoon to scrape the avocado meat into a small bowl. Season with oregano, salt, and pepper and use a fork to mash the avocados (there should still be a few lumps left). Next, pour in the chopped sun-dried tomatoes and combine everything.
- Spread the avocado mix evenly on top of the mushrooms and drizzle with a finish of olive oil.
- Bake the avocados in the oven for 25-minutes or until they are golden on the outside and cooked all the way through to tenderness.
- Serve with a topping of soft onions and enjoy.
Making portobello avocado steaks on the grill
- Heat the grill.
- Clean the portobello mushrooms and place them with the stem side up on a plate.
- Use a spoon or butter knife to spread a generous layer of red pesto on top of the mushrooms. Cut the avocados in half and carefully remove the stones without cutting yourself. Use a spoon to scrape the avocado meat into a small bowl. Season with oregano, salt, and pepper and use a fork to mash the avocados (there should still be a few lumps left). Next, pour in the chopped sun-dried tomatoes and combine everything.
- Spread the avocado mix evenly on top of the mushrooms and drizzle with a finish of olive oil.
- Grill the avocados for 15-20 minutes or until they are grilled golden with darker char marks and cooked all the way through to tenderness.
- Serve with a topping of soft onions and enjoy.


What to serve with portobello mushroom steaks
- Easy creamy BBQ potato salad
- Healthy oven-roasted carrot fries
- Oven-baked crispy potato wedges
- Authentic Spanish White bean salad
- Quick Mediterranean Spicy Bean salad
- Super crispy polenta fries
- Vegan black bean Cowboy caviar
- Easy authentic vegan Swedish potato salad
Ways to serve portabella mushrooms
There are so many delicious ways to serve portobello mushrooms. Here are three of my favorites;
- As a delicious juicy burger or sliders
- Topped on a creamy bed of mashed potatoes
- With a side of salad and fries
Frequently Asked Questions
Absolutely. You can use any type of pesto you prefer.
My personal favorite vegan pesto is the vegan red pesto you can find in my FREE 5 Fave spice mixes + 5 best vegan sauces and dips guide you get when you sign up for my newsletter. It’s THE rich, luxe vegan pesto that I use on EVERYTHING. From sandwiches to these portobello steaks pesto is my go-to.
Yes. Nearly all mushrooms are freezer friendly. You can freeze these mushroom steaks before or after they are made. Just make sure to heat them all the way through before serving.
Absolutely. Guacamole will work just as well as mashed avocados.
Easy Vegan portobello avocado steaks
Ingredients
- 2 tbsp Olive Oil
- 4 large Portobello Mushrooms
- 4 tbsp Vegan Red Pesto
- 2 Avocados mashed with a fork
- 4 Oil packed Sundried Tomato halves chopped
- 1 tsp Oregano
- ½ tsp Sea salt or Kosher Salt
- Pinch of Pepper
Caramelized onions
- 2 tbsp Olive Oil
- 2 large Yellow Onions sliced
- ½ tsp Salt
- ½ tsp Pepper
Instructions
How to make Caramelized onions
- Heat olive oil in a pan. Once the pan is hot gently transfer the sliced onions to the pan and stir.
- Season with salt and pepper and let the onions cook at medium-high heat while stirring occasionally. The onions should cook for 15-minutes or until they are soft, Caramelized in places, and tender. Add extra salt if needed before serving.
Making portobello avocado steaks in the oven
- Preheat the oven to 400F.
- Clean the portobello mushrooms and place them with the stem side up in a baking pan. Use a spoon or butter knife to spread a generous layer of red pesto on top of the mushrooms.
- Cut the avocados in half and carefully remove the stones without cutting yourself. Use a spoon to scrape the avocado meat into a small bowl. Season with oregano, salt, and pepper and use a fork to mash the avocados (there should still be a few lumps left). Next, pour in the chopped sun-dried tomatoes and combine everything.
- Spread the avocado mix evenly on top of the mushrooms and drizzle with a finish of olive oil.Bake the avocados in the oven for 25-minutes or until they are golden on the outside and cooked all the way through to tenderness.Serve with a topping of soft onions and enjoy.
Making portobello avocado steaks on the grill
- Heat the grill.
- Clean the portobello mushrooms and place them with the stem side up on a plate. Use a spoon or butter knife to spread a generous layer of red pesto on top of the mushrooms.
- Cut the avocados in half and carefully remove the stones without cutting yourself. Use a spoon to scrape the avocado meat into a small bowl. Season with oregano, salt, and pepper and use a fork to mash the avocados (there should still be a few lumps left). Next, pour in the chopped sun-dried tomatoes and combine everything.
- Spread the avocado mix evenly on top of the mushrooms and drizzle with a finish of olive oil.Grill the avocados for 15-20 minutes or until they are grilled golden with darker char marks and cooked all the way through to tenderness.Serve with a topping of soft onions and enjoy.