This post may contain affiliate links. Read my disclosure policy.
These baked stuffed portobello mushrooms are filled with spinach, Gruyère, Parmesan, and breadcrumbs. Easy, elegant, and ready in 45 minutes. Perfect vegetarian appetizer or side dish.
Baked Stuffed Portobellos (with Spinach, Parmesan, and Gruyère Cheese)
I love mushrooms, and I have quite a few popular vegetarian mushroom recipes on my site - like Hungarian mushroom soup and mushroom-and-spinach ravioli. Today I'm introducing you to my new favorite vegetarian main (or steakhouse-style side, depending on how you serve it)!
First, I par-bake the mushroom caps to draw out excess moisture. Then I stuff those big portobello caps with a savory mixture of sautéed onion, garlic, fresh thyme, wilted spinach, breadcrumbs, and a blend of Gruyère and Parmesan. The stuffed mushrooms go back in the oven until the tops are golden and the cheese is bubbling.
It's super easy, quick, and fancy - like something you would order at a nice restaurant to go alongside your ribeye steak or filet mignon.
Serve stuffed portobello mushrooms as an appetizer, a hearty vegetarian main, or an impressive side dish for entertaining. It's perfect for Meatless Monday, holiday dinners, or anytime you want something meatless that still feels substantial.
What Makes This Recipe Stand Out
- I pre-bake the caps first: That first 15-minute bake lets the mushrooms release water so the final stuffing stays rich and not soggy - huge difference in texture.
- Gruyère and Parmesan are a winning combination. Gruyère melts into a creamy, nutty layer while Parmesan crisps the top golden.
- Vegetarian, and easy to make gluten-free by using gluten-free bread crumbs.
- Easy enough for a weeknight, impressive enough for guests. Everything comes together in about 45 minutes with one skillet and one baking sheet.
Ingredients and Substitutions
- Portobello mushrooms: I use large caps - the bigger the better. Look for ones that are firm and dry, not slimy. Baby bellas won't work here; you need the volume.
- Breadcrumbs: You can use store-bought or homemade. I prefer making my own using slightly stale white bread - two small slices with the crusts removed will yield the perfect amount.
- Cheese: I chose Gruyère and Parmesan for their excellent melting quality and rich, nutty flavor. If you prefer a milder cheese, mozzarella makes a great substitute. Other options include feta, goat cheese, cheddar, and Pecorino Romano.
- Onion: I use half a yellow onion, finely diced, so it disappears into the filling. White onion works just as well. If you only have shallots, use two - they're milder but work nicely here.
- Fresh spinach: I use fresh, chopped spinach. It wilts down to almost nothing, so don't be alarmed by the volume before cooking. Frozen spinach works if you thaw and squeeze it very dry first. If you don't, any extra water will make the filling soggy.
- Garlic: I always use fresh, minced garlic.
- Fresh thyme: If you don't have fresh, use half the amount of dried. Dried thyme is more concentrated and can turn bitter if you use too much.
- Olive oil: I use regular olive oil for the sauté.
Expert Tip for Prepping Mushrooms
I usually scrape out the dark mushroom gills because it gives me more room to stuff and helps prevent extra moisture from seeping out as the portobello mushrooms bake. It also keeps the filling looking cleaner and more appetizing (those gills can darken the inside a bit). However, if you enjoy the bold, earthy taste of mushrooms, you can leave the gills intact - just keep in mind that the finished dish may turn out slightly more watery.
Variations
- Add Protein: Stir in cooked Italian sausage or chopped crispy bacon to make stuffed mushrooms more substantial.
- Make It Spicier: Add red pepper flakes or a pinch of cayenne to the filling.
- Creamier Filling: Mix in a spoonful of cream cheese or ricotta for a softer, richer center.
- Gluten-Free: Use gluten-free breadcrumbs or finely ground almonds for texture.
Serving Ideas:
These stuffed mushrooms are versatile enough to fit into almost any meal. Here's how I recommend serving them:
- Classic pairings: Serve with crusty sourdough bread or rustic seeded rye bread, my green beans with pine nuts, homemade garlic rolls, or my bread machine loaf. Stuffed portobello mushrooms also pair well with my apple spinach salad and creamy broccoli cashew salad.
- As an appetizer or starter: Serve one or two caps per person before a larger main. They work really well before something rich like braised short ribs or beef bourguignon, especially when you want a vegetarian-friendly starter.
- As a light vegetarian main: Two caps per person with a simple green salad and crusty bread. A tomato-cucumber-avocado salad or a beet-and-spinach salad with mandarin oranges works beautifully alongside.
- As a side dish: Serve one cap per person alongside my filet mignon, pan-seared marinated steak, baked stuffed pork tenderloin, Hawaiian grilled teriyaki chicken skewers, or grilled salmon. They also fit naturally on a holiday table next to roasted meats like my roast duck.
- Leftovers can be chopped and folded into pasta, spooned over polenta, or tucked into a toasted sandwich with extra cheese.
Portobello Stuffed Mushrooms
These baked Portobello Stuffed Mushrooms are my go-to when I want something that tastes restaurant-quality but still works for a weeknight dinner. Each meaty mushroom cap is loaded with a savory filling of spinach, garlic, Gruyère, Parmesan, and breadcrumbs, then baked until golden and bubbly.
Ingredients
- 4 large Portobello mushrooms
- 2 tablespoons olive oil
- ½ small onion finely diced
- 2 cloves garlic minced
- 2 sprigs fresh thyme stalks removed
- 2 cups fresh spinach chopped
- ½ cup breadcrumbs
- ½ cup Gruyère cheese shredded
- ¼ cup Parmesan cheese grated
- 2 tablespoons fresh parsley finely chopped
- salt and pepper to taste
Instructions
Pre-Cook Mushrooms
- Preheat the oven to 375ºF. Line a baking sheet with parchment paper and set aside.
- Wipe the mushrooms clean with a damp paper towel. Remove the stalks from the mushrooms, finely chop them and save for later. Scrape the gills from inside the mushrooms and discard.
- Place the mushrooms on the baking sheet, open side up. Cook in the oven for 15 minutes after which time the mushrooms will have expelled some water/juice which can be reserved for later.
Make the Filling
- Place a skillet or cast iron dish over a medium heat, and add the oil. When the oil is hot add the onion and sauté for about 2 minutes until soft, then add the garlic, chopped mushroom stalks and thyme, then cook for another minute.
- Stir in the chopped spinach and juice from the cooked mushrooms. Cook for 1-2 minutes until the spinach has wilted then remove from the heat.
- To the dish, add the breadcrumbs, Gruyère and Parmesan. Season with salt and pepper and mix until well combined.
Assemble & Bake
- Divide the mixture between the mushrooms, pressing it down gently into the caps.
- Bake for 15-20 minutes, or until the mushrooms are tender, the cheese is melted and the the tops are golden.
- Scatter over the chopped parsley, a few extra thyme leaves and a little extra parmesan to serve.
- Note: I provide helpful step-by-step photos below this recipe card. ⬇️⬇️
Notes
- For extra crunch, mix two tablespoons of breadcrumbs with two tablespoons of Parmesan and sprinkle over the mushrooms before baking.
- If you'd like some heat, stir in red pepper flakes with the filling. You could also enhance the texture by adding ¼ cup of chopped nuts, such as walnuts or hazelnuts.
- Finish with a quick broil (optional but amazing): If your tops aren't golden enough, a 1-2 minute broil gives that crisp, bubbly finish. Watch closely!
- Why are my stuffed mushrooms watery? Usually, it's one of three things: the caps weren't pre-baked long enough, the spinach/onion mixture wasn't cooked down, or the mushrooms were rinsed/soaked. Wipe mushrooms dry with paper towels, pre-bake, and drain. Sauté the filling until it looks "dry-ish" before adding cheese and crumbs.
- Can I make these gluten-free? Yes. You can swap in gluten-free breadcrumbs or crushed gluten-free crackers. Panko-style GF crumbs also work great.
- Can I make these ahead of time? Yes. You can make the filling up to 2 days ahead and store it covered in the fridge. You can also par-bake the caps, cool them, and refrigerate overnight. When you're ready to serve, stuff and bake for 15-20 minutes. If assembling fully ahead, refrigerate for up to 24 hours and add a few extra minutes to the bake time.
Storage Tips
- Fridge: Let the stuffed portobello mushrooms cool completely, then store them in an airtight container in the refrigerator for up to 3 days.
- Freezing: I don't recommend it as the mushrooms tend to release a lot of water after freezing and thawing, which can make the caps and filling soft and soggy.
- Reheating: Place mushrooms on a baking sheet and warm in a 350ºF oven for 10-15 minutes, until heated through and the tops are lightly crisp again.
Nutrition
Nutrition Information
Portobello Stuffed Mushrooms
Amount per Serving
Calories
237
% Daily Value*
Fat
15
g
23
%
Saturated Fat
5
g
31
%
Trans Fat
0.003
g
Polyunsaturated Fat
1
g
Monounsaturated Fat
7
g
Cholesterol
22
mg
7
%
Sodium
338
mg
15
%
Potassium
468
mg
13
%
Carbohydrates
15
g
5
%
Fiber
2
g
8
%
Sugar
4
g
4
%
Protein
11
g
22
%
Vitamin A
1804
IU
36
%
Vitamin C
9
mg
11
%
Calcium
292
mg
29
%
Iron
2
mg
11
%
* Percent Daily Values are based on a 2000 calorie diet.
Nutrition Disclaimer:
The nutritional information on this website is only an estimate and is provided for convenience and as a courtesy only. The accuracy of the nutritional information for any recipe on this site is not guaranteed. It should not be used as a substitute for a professional nutritionist's advice.
Step-by-Step Photos for Stuffed Portobellos
- Preheat the oven to 375ºF and line a baking sheet with parchment.
- Prep mushrooms: Clean mushrooms, remove/chop stems, then scrape out the gills (optional; it gives you more room to fill and helps prevent a watery result).
- Roast caps open-side up for 15 minutes, then drain/save any liquid.
- Sauté onion in oil 2 minutes.
- Add garlic, chopped stems, and thyme 1 minute.
- Stir in spinach plus a splash of the mushroom liquid; cook just until wilted.
- Off heat, mix in breadcrumbs, Gruyère, and Parmesan; season.
- Spoon the mixture into the mushroom caps, pressing it in gently.
- Bake for 15-20 minutes, until the mushrooms are tender and the tops are melted and golden.
- Top with parsley and extra Parmesan.
Submit your question or provide a review of the recipe + star rating RIGHT HERE.