Disclosure: This post may contain affiliate links. I may earn a small commission for my endorsement, recommendation, testimonial, and/or link to any products or services from this website.
This cheesy and flavorful vegetarian lasagna is the essence of fall! The decadent butternut squash lasagna includes a whipped roasted butternut squash sauce, sauteed mushrooms and onions, spinach, three different types of cheese, and earthy herbs like sage and thyme. It’s a delicious casserole for cozy Sunday evenings, or a satisfying, meat-free option for your Thanksgiving table.
Vegetarian Butternut Squash Lasagna
A warm and hearty butternut squash lasagna is the perfect vegetarian casserole for the cool weather months. Whether you assemble it on a lazy Sunday afternoon, or prepare it in advance for a special meatless Thanksgiving entrée, this cozy dish is sure to please both meat-lovers and vegetarians alike. It’s loaded with fresh autumn flavor, thanks to the roasted butternut squash, sauteed mushrooms and onions, spinach, and fresh herbs — and it’s totally decadent, thanks to plenty of ooey, gooey, melty cheese.
While I typically prefer quick-prep dinners that don’t require too many ingredients, steps, or dishes, there are a handful of meals that I deem “worth it” to spend a bit more time in the kitchen. Nothing about this lasagna is difficult, but there are a few different components that make it more time-consuming than other recipes in my arsenal. Trust me when I say, you won’t be sorry that you devoted a couple of hours to this one! Assemble it in advance for a holiday meal, or prep it on the weekend to reheat for weeknight leftovers. It’s the perfect addition to your harvest feast!
This is just a quick overview of the ingredients that you’ll need for a pan of butternut squash lasagna. As always, specific measurements and complete step-by-step cooking instructions are included in the printable recipe box at the bottom of the post.
- Butternut squash: you’ll need one large squash for this recipe, which typically weighs between 3 ½ – 4 pounds.
- Olive oil: for roasting the squash.
- Milk: to thin the butternut squash puree so that you can turn it into a whipped, spreadable sauce.
- Thyme and sage: fresh autumnal herbs that lend an earthy flavor to the casserole and pair beautifully with the winter squash, mushrooms, and onions.
- Salted butter: for sauteing the mushrooms and onions. You could use olive oil, but the butter gives the vegetables so much rich flavor.
- Onions and mushrooms: more veggies that add flavor and bulk to the vegetarian lasagna. I love the “meaty” texture of baby portabella mushrooms, but white button mushrooms are also fine.
- Frozen chopped spinach: thawed and squeezed really dry in a dish towel so that you don’t end up with a watery lasagna filling.
- Ricotta cheese: adds a thick, creamy, cheesy layer to the dish. You can substitute with small curd cottage cheese for a lighter option.
- Mozzarella cheese and Parmesan cheese: these additional cheeses add flavor to the casserole and hold it all together. The more cheese the better, right?!
- Egg: helps bind the ricotta cheese layer so that it doesn’t ooze out when you slice the casserole.
- Garlic powder and ground nutmeg: add even more flavor to the dish.
- No-boil (“oven-ready”) lasagna noodles: these par-boiled noodles do not require boiling before you assemble the casserole.
- Kosher salt and ground black pepper: to enhance the rest of the ingredients.
Can I use fresh spinach in lasagna instead of frozen spinach?
Yes, but you will need a lot of fresh spinach! The beauty of frozen chopped spinach is that it’s already condensed, so you get a large amount of spinach at a very inexpensive price — and you don’t need to cook it before adding it to the ricotta mixture.
If you prefer to substitute with fresh spinach, a 10 oz package of frozen spinach is the equivalent of about a 1 pound bunch of fresh spinach. If you’re buying fresh spinach, it’s wise to buy more than you think you’ll need because some bunches will need the stalks trimmed off and that will decrease the weight before cooking. You’ll also need to cook the fresh spinach, drain it, and squeeze out the excess liquid before adding it to the cheese mixture.
How to Make Butternut Squash Lasagna
While this lasagna requires multiple preparation steps before assembling the casserole, none of these components are difficult at all. It’s the perfect cozy, veggie-forward dish for a quiet evening at home. Best of all, you’ll have a big pan of leftovers to reheat and enjoy throughout the week!
- Roast the butternut squash until very fork tender, and then puree the flesh in a blender or food processor with milk, herbs, salt, and pepper.
- Sauté the mushrooms and onions in a large skillet with butter and herbs.
- Stir together the spinach and cheese mixture.
- Assemble the casserole by layering the no-boil lasagna noodles with the squash sauce, mushrooms and onions, spinach, and cheese.
- Sprinkle the top with additional cheese, cover with foil, and bake in a 400°F oven for 25 minutes. Remove the cover and bake for about 15 more minutes, until the filling is hot and bubbly and the cheese on top is nicely browned.
- Let the lasagna rest for at least 15 minutes before slicing and serving. Garnish with additional fresh herbs, if you like.
This hearty, homemade vegetarian lasagna is delicious when paired with a Caesar salad, a shaved fennel salad, a fall salad with maple balsamic dressing, or a simple green salad dressed in red wine vinaigrette. You might also like to offer a side of garlic bread, homemade focaccia bread, Southern cornbread, pumpkin bread, pumpkin muffins, cranberry bread, or cranberry muffins to complete the meal.
Assemble the lasagna in advance, but do not bake it. Wrap the dish tightly with plastic wrap and aluminum foil. Store it in the refrigerator for up to 48 hours before baking, or freeze the dish for up to 3 months.
When ready to bake, allow the refrigerated lasagna to sit on the counter and come to room temperature for at least 30-60 minutes before baking. If you’re baking a frozen lasagna (directly from the freezer), bake the dish covered in a 400°F oven for 1 hour. Then remove the cover and bake for an additional 10-15 minutes (or until the pasta is tender and the dish is heated through).
Leftover lasagna will keep in an airtight container in the refrigerator for 3-4 days. You can also freeze the leftovers in an airtight container for up to 3 months.
How to Reheat
Cover the lasagna loosely with foil. Warm the dish in a 350°F oven just until heated through, about 30 minutes. You can also reheat individual slices of lasagna in the microwave until warm, about 30-60 seconds.
- I prefer ricotta cheese because it has a thicker, smoother, creamier texture than cottage cheese. For a lighter choice, you can substitute with small curd or whipped cottage cheese. If the cottage cheese looks like it has a lot of liquid, strain it before combining it with the rest of the ingredients. Cottage cheese is saltier than ricotta, so you can decrease the salt called for in the recipe as well.
- If you’re feeling adventurous, try making your homemade lasagna from scratch with homemade lasagna noodles.
- When using homemade lasagna noodles or boiled lasagna noodles (rather than the no-boil noodles), reduce the oven temperature to 375°F.
- Cooking for Two? Divide the full recipe between two smaller 8-inch square baking dishes. That way you get two meals with the same amount of effort, and you can freeze one for a later date. Alternatively, you can cut all of the ingredients in half and prepare one lasagna in an 8-inch square dish. The baking instructions remain the same.
Tips for the Best Butternut Squash Lasagna Recipe
- The egg is an important component of the ricotta mixture because it helps the cheese layer “set” so that it doesn’t ooze out when you slice into the casserole. That said, if you have an egg allergy, you can omit this ingredient — the finished texture just won’t be quite the same.
- Use whole milk ricotta cheese for the richest, creamiest, smoothest texture.
- Let the lasagna rest for at least 10-15 minutes before slicing. This will help the cheese set so that it slices cleanly and doesn’t ooze out.
- Taste and season as you go. Each layer of the lasagna is an opportunity to add flavor to the dish. For instance, taste the butternut squash sauce, and add extra salt, pepper, or herbs to your liking. Similarly, add extra seasoning or herbs to the mushrooms and onions to suit your preferences. Make it your own!
- Garnish each slice of lasagna with chopped fresh herbs, additional grated Parmesan cheese, or crushed red pepper flakes (for a little bit of spice)!
Roasted Butternut Squash Lasagna
FOR THE BUTTERNUT SQUASH LAYER:
- 1 (large) butternut squash (about 3 ½ – 4 pounds)
- 1-2 tablespoons olive oil
- ⅔ cup milk
- 1 teaspoon fresh thyme leaves (or ½ teaspoon dried thyme leaves)
- 2 fresh sage leaves (or ¼ teaspoon dried sage)
- ¾ teaspoon kosher salt
- Dash of ground black pepper
FOR THE MUSHROOM LAYER:
- ¼ cup (½ of a stick) salted butter
- 2 large yellow onions, thinly sliced
- 8 ounces sliced baby bella mushrooms or white button mushrooms
- ½ teaspoon chopped fresh thyme leaves (or ¼ teaspoon dried thyme)
- 1 fresh sage leaf chopped (or ⅛ teaspoon dried sage)
- Kosher salt and ground black pepper, to taste
FOR THE RICOTTA SPINACH LAYER:
- 1 (10 ounce) package frozen chopped spinach, thawed
- 15 ounces ricotta cheese (or sub with 16 ounces small curd cottage cheese, extra liquid strained)
- 1 cup shredded mozzarella cheese
- ¼ cup grated Parmesan cheese
- 1 large egg, lightly beaten
- ½ teaspoon salt
- ½ teaspoon garlic powder
- ⅛ teaspoon ground nutmeg
- 1 (12 ounce) package no-boil (“oven ready”) lasagna noodles (you probably will not need the entire box; I use 10 noodles total)
- 1 ½ cups shredded mozzarella cheese
- ¼ cup grated Parmesan cheese
- Optional garnish: chopped fresh parsley or other herbs
- Preheat oven to 400°F. Grease a deep 13 x 9-inch baking dish; set aside.
PREPARE THE BUTTERNUT SQUASH:
- Slice squash vertically down the center, and scoop out the seeds. Rub olive oil all over the squash, and place the halves cut-side down on a baking sheet lined with parchment paper. Roast in the oven for about 50-60 minutes, or until very tender.
- Allow squash to cool, peel the skin off, and transfer the flesh to a food processor or blender.
- Add the milk, thyme, sage, salt, and pepper. Blend until smooth; set aside.
PREPARE THE MUSHROOMS:
- Melt the butter in a large skillet over medium-high heat. Add the onions and saute until soft, about 8 minutes. Increase the heat to high, add the mushrooms, thyme, and sage, and cook until tender, about 3 more minutes. Remove from the heat. Season with salt and pepper to taste. Set aside.
PREPARE THE RICOTTA SPINACH LAYER:
- Squeeze all of the liquid out of the spinach. I like to use a dish towel for this, and just keep squeezing until you wring out as much water as possible. Place spinach in a large bowl.
- Add ricotta, mozzarella, Parmesan, egg, salt, garlic powder, and nutmeg to the bowl with the spinach. Stir really well with a fork to combine.
ASSEMBLE THE LASAGNA:
- Spread about ¾ cup of the butternut squash mixture on the bottom of the prepared baking dish. Top with a layer of no-boil lasagna noodles (using as many as you need to cover a single layer in the dish), ½ of the ricotta mixture, and ½ of the mushroom mixture.
- Add a heaping 1 cup of the butternut squash mixture on top, another layer of noodles, the remaining ricotta mixture, and the remaining mushrooms.
- Spread any remaining butternut squash on top. Finish with 1 ½ cups of shredded mozzarella cheese and ¼ cup of grated Parmesan cheese.
- Cover the dish with foil.
- Bake for 25 minutes. Remove the cover and bake for about 15 more minutes, until the filing is hot and bubbly and the cheese on top is nicely browned.
- Let stand for at least 15 minutes before slicing and serving. Garnish with additional chopped fresh herbs, if desired.