Today I am sharing a favorite mushroom lasagna recipe made with caramelized onion and portobello mushrooms. It is so satisfying, even meat lovers will love this comfort food classic. It is made with part-skim ricotta and shredded cheese and can be made two days ahead.

Vegetarian Caramelized Onion and Portabella Mushroom Lasagna

Why We Love This Portobello Mushroom Lasagna Recipe

I have been meaning to make you all another lasagna- since the time I shared my beef and spinach lasagna. I decided to keep this one vegetarian, and to add in my favorite meatless substitute: portobello mushrooms.

The recipe came out amazingly well, even for meat-eaters. The savory caramelized onions and “meaty” portobello mushrooms make this lasagna hearty and satisfying. Serve it as a Sunday meal or as a make-ahead dinner when you won’t have time to prep during the week. We have more details below about how to prep this ahead.

This combination is so good! We sautéed sweet onions and portobello mushrooms until the onions were incredibly soft and caramelized. Then added in chopped fresh herbs including sage, rosemary and thyme in it.

If you love Portobello Mushrooms as much as we do, make sure to check out our recipe for Simple Roasted Portobellos and these Easy Sauteed Portobello Mushrooms. They’re a great addition to so many vegetarian meals. And if you love vegetarian lasagnas, also be sure to check out my Vegetable Lasagna Primavera too. It’s loaded with fresh veggies and spinach!

Vegetarian Caramelized Onion and Portabella Mushroom Lasagna in a white baking dish


Ingredients for Vegetarian Caramelized Onion and Portabella Mushroom Lasagna
  • Lasagna noodles or oven ready lasagna noodles: I tested it with both the oven-ready lasagna noodles and with the traditional kind that you have to boil. Both worked easily, but I loved the convenience of no-boil noodles! Bonus: one less dish to wash!
  • 1 tablespoon extra-virgin olive oil
  • 2 large sweet onions, sliced
  • ¾ teaspoon salt
  • 2 6-ounce packages of Portobello Mushroom caps, halved and sliced (gills removed if desired)
  • 2 tablespoons chopped Fresh mixed herbs (Poultry Blend): Go easy on the rosemary; while delicious and a great match for mushrooms, rosemary is very bossy and can take over the flavors of the dish. I used more sage and thyme- and only about a total of 1 ½ teaspoons of rosemary in the overall blend.
  • 1 large egg
  • 1 16-ounce container part-skim ricotta cheese
  • ½ teaspoon ground pepper
  • 1 26-ounce jar Pasta Sauce
  • 2 cups (8- ounces) shredded Mozzarella
  • 3 tablespoons shredded Parmesan cheese
Vegetarian Caramelized Onion and Portabella Mushroom Lasagna in baking dish on a cutting board

Tips on How to Make Portobello Mushroom Lasagna

Here are some tips and things you’ll want to keep in mind while making this recipe. I recommend reading it through first so that you can stay organized in the kitchen. 

Caramelized Onions and Portabella Mushrooms in a pan

Pre-cook the veggies — You never want to add raw vegetables directly into the mushroom lasagna. Not only will the veggies release a lot of water and potentially make the vegetable lasagna soggy, but they also won’t cook through all the way in the oven. To make sure your lasagna is easy to slice and serve and is cooked all the way through, caramelize the onions and sauté the mushrooms before building your lasagna. Trust me, it’s worth the extra few minutes of prep work!

Spread pasta sauce on the bottom of the baking dish — To prevent the noodles from sticking to the baking dish, you should spread a thin layer of sauce along the bottom of the dish. You don’t need much, just half a cup or so.

Don’t overfill the layers — I know it’s tempting to really load up every layer of the lasagna, but if you do that your lasagna will be far too heavy and impossible to serve. Remember: your lasagna has lots of layers, so a little ricotta and sauce in each layer will go a long way.

Bake with foil on top — Cook the lasagna most of the way with foil on top of the baking dish. This will ensure the lasagna heats through as fast as possible andthe noodles will soften properly. Plus the foil will prevent the noodles from drying out and the top from browning in the oven too quickly. Near the end of the baking time, remove the foil and sprinkle on a little cheese and cook a little longer until the top is golden and bubbly.

How to Freeze Lasagna

Mushroom lasagna freezes surprisingly well and is super easy to reheat later on. To freeze lasagna, you first need to assemble and bake it as you normally would. Omit the cheese on top! Then, let it cool to room temperature you can freeze the entire lasagna whole. Just wrap it in two layers of plastic wrap. If you have an extra-large re-sealable bag, slide the lasagna into it. That will help prevent freezer burn. If you don’t have an extra-large freezer bag, wrap the lasagna in foil. TO defrost the lasagna, set in the fridge and let defrost for two days before reheating, covered in the oven set at 325 degrees F. Once it is heated through, increase the heat to 35o, add the cheese on top and continue baking.

If you prefer to freeze individual servings, cut the cooked lasagna into slices and transfer them to re-sealable containers. Freeze up to 6 weeks. To reheat the lasagna slices, pop the frozen slices into a warm oven and cook until heated through. This will take more than a half hour since it is frozen through, so have patience. Check with an instant read thermometer to make sure it is over 145 degrees before serving.

Make Ahead Tips For Mushroom Lasagna

I also tested making the mushroom lasagna ahead of time, and it was so easy. I built it, refrigerated it two days and then baked it! I couldn’t believe how well that worked and will have to keep that in mind for those times when working ahead is necessary. {Hello holiday house guests!}

Vegetarian Caramelized Onion and Portabella Mushroom Lasagna

More Italian Recipes:

More Healthy Mushroom Recipes

At Healthy Seasonal Recipes, we specialize in cooking with fresh veggies and creating weeknight meals. Sign up HERE to get more produce-forward dinner ideas for FREE! If you make this recipe, please come back and leave a star rating and review. I would love to hear what you thought! Happy Cooking! ~Katie

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Caramelized Onion and Portabella Mushroom Lasagna #lasagna #italianfood #lasagnarecipe

Portobello Mushroom Lasagna

5 Stars 4 Stars 3 Stars 2 Stars 1 Star

5 from 5 reviews

  • Author: Katie Webster
  • Total Time: 1 hour 45 minutes
  • Yield: 8 1x


This vegetarian portobello mushroom lasagna is made with savory caramelized onions, part-skim ricotta and shredded cheese, and can be made two days ahead.


Units Scale
  • 9 lasagna noodles or oven ready lasagna noodles
  • 1 tablespoon extra-virgin olive oil
  • 2 large sweet onions, sliced
  • 3/4 teaspoon salt
  • 2 6ounce packages Portobello Mushroom caps, halved and sliced (gills removed if desired)
  • 2 tablespoons chopped Fresh mixed herbs (look for a mixed package such as Poultry Blend)
  • 1 large egg
  • 1 16ounce container part-skim ricotta cheese
  • 1/2 teaspoon ground pepper
  • 1 26ounce jar Pasta Sauce
  • 2 cups (8- ounces) shredded Mozzarella
  • 3 tablespoons shredded Parmesan cheese


  1. If using regular noodles, bring a large pot of lightly salted water to a boil. (Skip to step 2 if using oven ready noodles.) Cook lasagna, stirring occasionally according to package instructions or until al dente. Drain and rinse with cold water.
  2. Meanwhile, heat oil in a large skillet over medium heat. Add onion and salt and cook, stirring occasionally (add 4 to 5 tablespoons water as necessary to prevent from browning before the onions become very soft) until browned and very soft, about 15 minutes. Stir in mushrooms, herbs. Increase heat to medium-high and continue cooking, stirring often, until the mushrooms have become soft and their liquid has evaporated, 5 to 7 minutes.
  3. Preheat oven to 350 degrees F. Coat a 9 by 13-inch baking dish with cooking spray.
  4. Beat egg in a medium bowl. Add ricotta and pepper and stir until completely combined.
  5. Spread ½ cup pasta sauce in the bottom of the prepared baking dish. Layer three cooked lasagna noodles vertically into the baking dish. Top with half of the onions and mushroom mixture. Spread with about half of the ricotta mixture. Top with ¾ cup sauce and 2/3 cup shredded mozzarella.
  6. Layer on 3 more noodles, the remaining onion mixture, the remaining ricotta mixture, 3/4 cup sauce and 2/3 cup cheese.
  7. Top with the remaining 3 noodles and the remaining ¾ cup sauce. Cover with aluminum foil.
  8. Bake until the lasagna is steaming hot all the way through, 38 to 45 minutes. Remove foil, sprinkle with the remaining 2/3 cup shredded mozzarella and Parmesan. Bake until the mozzarella on top is just melted but not browned, about 10 minutes.
  9. Let lasagna cool 10 to 15 minutes before slicing it into 8 servings.


To Make Ahead: Can be prepared through step 5 up to 2 day in advance. Proceed with step 6 adding an extra 15 minutes of cook time before removing foil.

  • Prep Time: 35 minutes
  • Cook Time: 50 minutes
  • Category: Main Course
  • Method: Baked
  • Cuisine: Italian


  • Serving Size: 1/8 lasagna
  • Calories: 324
  • Fat: 13
  • Carbohydrates: 32
  • Fiber: 3
  • Protein: 22