Loaded with savory roasted vegetables and melted provolone cheese, this Portobello Mushroom Sandwich is so satisfying even meat-eaters will love it. Perfect for your next Meatless Monday!
We’ve shared a lot of sandwich recipes on the site but I think this Portobello Mushroom Sandwich might be my all-time favorite. In the last month, Tim and I have made it over 5 times and we’re still not sick of it.
A few things that make this a great weeknight dinner recipe:
- Everything is toasted and roasted in the toaster oven, so it’s EASY to throw together.
- Lots of yummy veggies: juicy portobello mushroom, sweet roasted onion, and crisp bell pepper. (I love the slight bitterness of green peppers but you can use a sweeter red, orange, or yellow pepper instead.)
- It’s loaded with a CRAZY amount of salty, earthy, rich umami flavor.
If you’ve tried one of our other vegetarian sandwiches, like this popular Roasted Red Pepper, Carrot and Hummus Sandwich a Grilled Cheese with Apple and Havarti, or any of these 20 Healthy Vegetarian Sandwiches then you know we take our sandwich game pretty seriously.
And these cheesy mushroom melts are no exception. They’re incredibly delicious and you NEED to make them tonight.
~ Keep scrolling for step by step photos & tips after the recipe ~
How to Make A Portobello Mushroom Sandwich
STEP 1: Toast Your Rolls While You Preheat
Start by lowering the rack in your toaster oven to the bottom position, place your rolls (unsplit) on the rack and preheat to 425°F on the BAKE setting.
One of the best parts of this sandwich is the rolls – they’re crunchy and toasted outside but soft and warm inside. To achieve this awesomeness, just warm and toast the rolls while your little oven preheats.
If your toaster oven only has a traditional temperature dial, set a timer for about 4 to 5 minutes.
STEP 2: Make the Marinade
The quick marinade for the vegetables is simple: olive oil, balsamic vinegar, soy sauce, and a few spices. To make it, dump everything in a large bowl and whisk together.
Add the mushrooms to the marinade solo, this gives them a chance to soak up most of it first. Then toss in the pepper and onion slices.
Lastly, rub a rimmed sheet pan with a little oil and pour the veggies onto it.
STEP 3: Roast The Vegetables
Right about now, the toaster oven should beep that it’s ready. Remove the rolls, set them aside, and add the vegetables.
Stir the pan once or twice while it cooks. Around the 7 minute mark, the mushrooms will begin to release a lot of liquids and your house will start smelling very good.
After about 15 to 18 minutes a little of the liquid will remain but the onions, mushrooms, and peppers will be brown on the edges and have a delicious tender-yet-toothy texture.
STEP 4: Get Melty
Put on a pair of oven mitts and carefully remove the hot pan. Use a spatula to scooch the roasted vegetables into two piles and top each one with a slice of smoky provolone cheese.
To melt the cheese, return the pan to the toaster oven for 2 to 3 minutes.
STEP 5: Assemble Your “Meaty” Meatless Sandwiches
Split the rolls in half and scoop the filling into each one. For a little spicy kick, sprinkle on a pinch of red pepper flakes. Then grab a few napkins, and enjoy!
Are You Cooking For One?
Toast a single roll and save half the roasted vegetables. You can use the leftover veggies to make a toaster oven frittata, throw them on a veggie hummus flatbread, or whip up another Portobello Mushroom Sandwich for lunch or dinner the next day.