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    Home Β» Vegetarian Β» Southwestern Casserole (Vegetarian)

    Southwestern Casserole (Vegetarian)

    May 11, 2022 Β· by Valentina Β· 37 Comments

    This post may contain affiliate links.

    Jump to Recipe

    This Southwestern Casserole is an amazing vegetarian comfort food. It’s layered with grilled zucchini, mushrooms, black beans, caramelized onions, and Latin flavors throughout.Southwestern Casserole with sliced avocado on top.

    Zucchini is one of the most versatile squashes, and it's incredibly delicious in so many recipes -- from fresh salads and stir-fries, to quick breads and chocolate cakes.

    We see it sliced, grated, chopped, grilled, roasted, sautΓ©ed, and so on.

    Along with a handful of other fresh ingredients, it's one of the stars of this delicious Southwestern Casserole.

    Raw sliced mushrooms, onions and zucchini on a sheetpan.

    Ingredients in Vegetarian Southwestern Casserole

    • zucchini
    • mushrooms
    • black beans
    • onion
    • garlic
    • jalapeΓ±o
    • chipotles in adobo sauce
    • cumin
    • cheddar cheese
    • pepper jack cheese
    • cilantro
    • avocado
    • olive oil, salt, pepper

    This is one very hearty vegetarian casserole, with a spicy Latin flavor profile. I think you’ll love it!

    How to Make this Southwestern Casserole

    - Slice zucchini thinly, lengthwise, about ΒΌ inch thick. (The easiest way to do this is to use a mandoline. If you don’t have one, use a Chef’s knife.) Zucchini being sliced into thin strips on a mandoline.

    - Coat the zucchini slices with olive oil and season them generously with salt and pepper. Add them to a very hot grill and cook until they're tender and nicely browned, about 2 minutes per side.Several slices of grilled zucchini on a sheet pan.

    - In a small bowl, combine jalapeΓ±o, garlic, chipotles in adobo sauce and cumin. (It's this, the beans and garnishes that really give this Southwestern Casserole its Latin vibe.)Small terra cotta bowl with mix of chopped peppers and garlic.

    - Add the onion to a large sautΓ© pan lightly coated with oil over medium heat. Cook until soft and golden, about 20 minutes. Then add the seasoning mixture, stir, and cook until aromatic, about 30 seconds. Caramelized onion, chopped garlic and peppers in saute pan.

    - Turn the heat up and add half of the mushrooms. Stirring often, sautΓ© until they’ve shrunk and softened, and then add the rest, and continue to cook until they're golden, about 10 minutes. Mix in the beans and season to taste with salt and pepper.Sauteed onions and mushrooms in saute pan with wooden spatula.

    - Assemble all of the prepared ingredients into a 9 x 13 x 2 inch baking dish as follows: β…“ of the onion-mushroom mixture, grilled zucchini, Β½ cup of the Cheddar and ΒΌ cup of the Pepper Jack cheese. Repeat this layering process twice more β€” however, the top layer of cheese will be ΒΎ cup of the Cheddar and Β½ cup of the Pepper Jack.Layers of grilled zucchini and mushrooms topped with grated cheese in casserole dish.

    - Place the baking dish in a preheated 375Β°F oven and bake for 20 minutes. Remove from the oven, cool a bit, and then garnish with cilantro, avocado and jalapeΓ±o slices.top view of baked grilled zucchini casserole, golden on top

    (More detailed instructions are in the recipe card below.)

    Recipe Tips and Substitutions

    • You can purchase pre-sliced mushrooms. (When they are pre-sliced you still need to wash them!)
    • Feel free to use yellow zucchini if you see it, and a combination of yellow and green would be pretty.
    • Grilling the zucchini adds a lot of the smoky flavor to this recipe. You can however, sautΓ© the zucchini in a cast iron skillet and it will acquire a lovely caramelization which also adds delicious flavor.
    • Avocado, cilantro and jalapeΓ±o slices are added to the top of the Southwestern Casserole for the garnish. It brightens up the whole dish and adds great fresh flavor. To save time, you can serve them on the side.
    • For more heat in this recipe, do not remove all (or any) of the jalapeΓ±o seeds.

    One serving of Grilled Zucchini Casserole on white plate with avocado on top

    Can you make it ahead?

    Yes! There are a couple options:

    • You can grill the zucchini and sautΓ© the vegetables up to one day ahead. About an hour before serving, assemble, bake and cool.
    • Take it one step further and assemble the casserole a day ahead of time. The next day, about 45 minutes before you want to serve, bake it. 

    Can you freeze it?

    Yes! Let it cool completely before freezing. It works very well to cut the casserole into portions, and then freeze them separately. This way, you can grab just enough for one or two, if you’d like.

    Be sure it’s wrapped very tightly to avoid air getting in. It can be frozen for up to three weeks. (I wouldn’t recommend freezing the whole casserole, but it’s great for leftovers.)

    I hope you love this Vegetarian Southwestern Casserole as much as my family and I do!

    More delicious vegetarian casseroles:

    • Smashed Potato Casserole
    • Lasagna with Swiss Chard
    • Vegetarian Potato Moussaka
    • Hatch Chile Cornbread Casserole
    Close up of one serving of Vegetarian Southwestern Casserole

    Vegetarian Southwestern Casserole

    Valentina K. Wein
    This Southwestern Casserole is an amazing vegetarian comfort food. It’s layered with zucchini, mushrooms, caramelized onion, and Latin flavors throughout.
    5 from 13 votes
    Print
    Prep Time 1 hr 15 mins
    Cook Time 20 mins
    Cooling Time 15 mins
    Total Time 1 hr 50 mins
    Course Main Course
    Cuisine American
    Servings 6
    Calories 349 kcal

    Equipment

    • mandoline slicer
    • stovetop grill

    Ingredients
      

    • 3 pounds zucchini, washed and dried
    • olive oil for the pan and coating the zucchini
    • 3 cups thinly sliced yellow onion
    • 6 tablespoons finely chopped jalapeΓ±o pepper, washed and dried, seeds removed,
    • 1 tablespoon minced garlic
    • 1 tablespoon finely chopped chipotles in adobo sauce,
    • 2 teaspoons ground cumin
    • 2 pounds (about 10 cups) Button or Crimini mushrooms, washed and dried, thinly sliced
    • 1ΒΎ cup cooked black beans, (from scratch or a can -- drain if from a can)
    • 1ΒΎ cup Cheddar cheese (white or orange), grated, divided
    • 1 cup Pepper Jack cheese, grated, divided
    • salt and freshly ground black pepper

    Garnishes

    • about 1 cup loosely packed cilantro leaves, washed and dried
    • about Β½ large avocado, thinly sliced
    • about 2 tablespoons thinly sliced jalapeΓ±o pepper, washed and dried

    Instructions
     

    • Prepare the zucchini: Slice about Β½ inch off the ends off of the zucchini and then slice them thinly, about ΒΌ inch. The easiest way to do this is to use a mandoline. (If you don’t have one, use a Chef’s knife. First cut a base by slicing off a thin strip from one side. Then with the zucchini sitting steady of this base, cut it into thin slices.)
    • Grill the zucchini: Preheat a stove-top grill (or outdoor grill). On a baking sheet, coat the zucchini slices with olive oil and season them generously with salt and pepper. Once the grill is hot, add the zucchini slices β€” there should be about an inch between them. Grill until they're tender and nicely browned, about 2 minutes per side. Set aside on a baking sheet to cool.
    • Preheat the oven to 375Β°F.
    • Prepare the seasonings: In a small bowl, combine the jalapeΓ±o, garlic, chipotles in adobo sauce, and cumin. Set aside.
    • SautΓ© the vegetables: Coat a large sautΓ© pan with olive oil and place it over medium heat. Add the onion and, stirring often, cook until soft and golden, about 20 minutes. Add the seasoning mixture, stir, and cook until aromatic, about 30 seconds. Turn the heat to medium-high, drizzle with a bit more olive oil and add about half of the mushrooms. Stirring often, sautΓ© until they’ve shrunk and softened, about 5 minutes. Add the second half of the mushrooms and continue to sautΓ© until all of the mushrooms begin to brown, about 10 minutes. Mix in the beans and season to taste with salt and pepper. (Here’s How to Season to Taste.)
    • Assemble: Add an even layer of the grilled zucchini slices to the bottom of a 9 x 13 x 2 inch baking dish. Cover this with an even layer of about β…“ of the mushroom-bean mixture. Sprinkle with Β½ cup of the Cheddar and ΒΌ cup of the Pepper Jack cheese. Repeat this layering process twice more β€” however, the top layer of cheese will be ΒΎ cup of the Cheddar and Β½ cup of the Pepper Jack.
    • Bake: Place the baking dish on a sheet pan and place in the preheated 375Β°F oven. Bake for 20 minutes. Remove from the oven and let it sit for about 15 minutes.
    • Garnish: After the 15 minutes of cooling time, garnish with the cilantro, avocado and jalapeΓ±o slices.
    • Serve!

    Notes

    Calorie count is only an estimate.
    Keywords grilled vegetables, Mexican dinner recipes, vegetarian comfort foods
    Have you tried this recipe?I'd love to see it on Instagram! Tag me at @cookingontheweekends or leave a comment & rating below.

    Cooking On The Weekends is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.

    More Vegetarian Recipes

    • Slow Cooked Red Cabbage Stew
    • Halloumi Fries with Greek Yogurt Dip
    • Easy Vegan Cream of Mushroom Soup
    • Crispy Smashed Cauliflower

    Reader Interactions

    Comments

    1. Marissa

      July 20, 2020 at 12:57 pm

      Everything about this grilled zucchini casserole is calling my name, Valentina! So many fresh and comforting flavors in one satisfying dish!

      Reply
      • valentina

        July 22, 2020 at 12:42 pm

        Thank you, Marissa. Enjoy! πŸ™‚ ~Valentina

        Reply
    2. Eha Carr

      July 20, 2020 at 5:29 pm

      As in Australia we are blessed with beautiful zucchini the year around and it happens to be one of my very favourite vegetables, my crisper is guaranteed to always have some waiting for inspiration. Your recipe is naturally interesting with its Tex-Mex suggestions more uncommon here. Eat avocadoes almost every day also . . . but shall have to pick another cheese. Personally I do not buy sliced mushrooms as, at least here, they tend to be not as fresh or of the top quality . . . I also never ever wash them . . . we are all different , , , Thanks !

      Reply
      • valentina

        July 22, 2020 at 12:44 pm

        Thank you, Eha. I eat avocados every day too. During the summer, at least. πŸ™‚ I can't get enough and seem to add them to almost everything lately. Enjoy! πŸ™‚ ~Valentina

        Reply
    3. angiesrecipes

      July 20, 2020 at 7:37 pm

      This is a GREAT recipe when the zucchini in season and so much better and healthier than lasagna .-))

      Reply
      • valentina

        July 22, 2020 at 12:45 pm

        Thanks, Angie. Yes, that's exactly what I attempting her -- a healthy and hearty lasagna of sorts. Enjoy! πŸ™‚ ~Valentina

        Reply
    4. Ron

      July 20, 2020 at 10:49 pm

      We love zucchini although we don’t see local grown that often. I guess they don’t like our climate. Ours mostly come from Italy and Spain.
      Great recipe idea, it has me thinking of veg nachos without the chip.

      Reply
      • valentina

        July 22, 2020 at 12:47 pm

        Ron, I love that comparison of the nachos!! Thank you. Hope all is well in your part of the world -- it's better than it is here for sure. Hoping California takes a turn for the better soon. In the meantime, I'll just keep cooking. πŸ™‚ ~Valentina

        Reply
    5. David @ Spiced

      July 21, 2020 at 4:44 am

      We have a ton of zucchini in the fridge right now - what a delicious way to use 'em up. Plus, grilled zucchini is delicious! πŸ™‚

      Reply
      • valentina

        July 22, 2020 at 12:48 pm

        Enjoy, David. Thanks so much for checking out the recipe. πŸ™‚ ~Valentina

        Reply
    6. Dawn- Girl Heart Food

      July 21, 2020 at 5:15 am

      What a fabulous comfort food meal! Love that zucchini is the star of the show. Would love a piece for supper tonight!!

      Reply
      • valentina

        July 22, 2020 at 12:49 pm

        Thank you, Dawn. Enjoy and hope all is well! πŸ™‚ ~Valentina

        Reply
    7. Priya

      July 21, 2020 at 8:20 am

      Grilled zucchini sounds really delicious. This casserole recipe is going to be our favorite for sure.

      Reply
      • valentina

        July 22, 2020 at 12:49 pm

        Thanks so much, Priya. Hope you love it! πŸ™‚ ~Valentina

        Reply
    8. David Scott Allen

      July 21, 2020 at 9:38 am

      I think I have everything on the list except the avocado and jalapeno - so I think I can live without those. We are buying a lot of squash at the market these days - this week it was all yellow squash. And I bought three bags of mushrooms (sliced) at Trader Joe's - it is as if I knew you were going to post this. Oh, and I will have to switch out something for the jack cheese - I have cheddar and Gouda. I am sure we will suffer that switch well. Will report back! The nice thing about this Dinner one night, and a couple of lunches to follow! (Leftovers for dinner in our house is verboten... by me! πŸ™‚

      Reply
      • valentina

        July 22, 2020 at 12:53 pm

        Oh I hope you love it, David! Thanks so much. The alterations you're making sound delicious! Enjoy and hope you and Mark are doing well. πŸ™‚ ~Valentina

        Reply
        • David Scott Allen

          July 29, 2020 at 6:22 pm

          It is in the oven with 4 minutes to go! It smells fantastic. For the mozzarella, w used a third each of mozzarella, Gouda, and La Vache Qui Rit. (Yes, I had that...) half the mushrooms, zucchini, and onions in am 8x8 pan. Yum!

          Reply
        • David Scott Allen

          July 29, 2020 at 6:50 pm

          O. M. G. β€” this is fabulous! Having seconds now.

          Reply
          • valentina

            July 31, 2020 at 11:51 am

            David, this makes me so happy!!! Thank you so much for sharing. πŸ™‚ ~Valentina xo

            Reply
    9. Kim Lange

      July 21, 2020 at 2:56 pm

      I love this recipe so much! I cannot wait to make it! My neighbor brought me some zucchini and this looks super amazing! TASTY & Pinning! πŸ™‚ Thanks for sharing.

      Reply
      • valentina

        July 22, 2020 at 12:54 pm

        Thanks, Kim. Luck you to have a neighbor who bring you fresh produce. Enjoy! πŸ™‚ ~Valentina

        Reply
    10. 2pots2cook

      July 22, 2020 at 3:16 am

      Beautiful vegetarian lasagna idea !!!! Absolutely keeper in our house πŸ™‚

      Reply
      • valentina

        July 22, 2020 at 12:54 pm

        Thanks, Davorka. Hope you and your family love it. Stay well! πŸ™‚ ~Valentina

        Reply
    11. Kathy @ Beyond the Chicken Coop

      July 22, 2020 at 5:52 am

      What a great dish and a great way to use up that garden zucchini! I love that you can make this now and freeze for later. Makes great sense to use while we have all this great zucchini!

      Reply
      • valentina

        July 22, 2020 at 12:57 pm

        Thanks, Kathy. Hope you love it! πŸ™‚ ~Valentina

        Reply
    12. Gerlinde

      July 22, 2020 at 7:14 am

      One can never have too many recipes for zucchini. I am growing my own zucchini this year and I can try your recipe with them. Thanks!

      Reply
      • valentina

        July 22, 2020 at 12:58 pm

        So lovely to be growing your own food. I love it. Thank you and enjoy! πŸ™‚ ~Valentina

        Reply
    13. Liz

      July 22, 2020 at 7:37 am

      Oh, my, I love everything about this yummy casserole! Since the picky husband won't eat zucchini OR mushrooms, it would be MY lunch all week long. I can't wait to give it a try.

      Reply
      • valentina

        July 22, 2020 at 12:56 pm

        Thanks so much, Liz. Hope you enjoy! πŸ™‚ ~Valentina

        Reply
    14. John / Kitchen Riffs

      July 22, 2020 at 7:45 am

      Love zucchini! In fact we're having it in a stir-fry tonight. Might have to rethink that plan and make this instead -- what a wonderful dish. I make something vaguely similar (kinda sorta the same concept, but the flavors are totally different), but really like how you've put together this recipe. Thanks.

      Reply
      • valentina

        July 22, 2020 at 12:55 pm

        Thanks so much, John. Hope you enjoy it -- or any variation of it. πŸ™‚ ~Valentina

        Reply
    15. Colette

      May 15, 2022 at 10:53 am

      Gorgeous! I'm always oozing for meatless, but tempting dishes abd this one's on the docket for Monday night! xo

      Reply
      • valentina

        May 19, 2022 at 10:29 am

        Hi Colette! Hope you and your family love it. πŸ™‚ ~Valentina

        Reply
    16. Kim Lange

      May 16, 2022 at 9:24 am

      Looks super amazing Valentina!! Pinning to make later!

      Reply
      • valentina

        May 19, 2022 at 10:26 am

        Thanks for checking them out, Kim. And for the pin. πŸ™‚ ~Valentina

        Reply
    17. 2pots2cook

      May 24, 2022 at 4:28 am

      Such a beautiful dish. Printing out to keep!

      Reply
      • valentina

        May 29, 2022 at 8:06 pm

        Yay. Hope you love it, Davorka. Thank you. πŸ™‚ ~Valentina

        Reply

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    Hi, I'm Valentina, certified chef, owner, recipe developer and photographer at Cooking on the Weekends. I'm also a mom of two boys and a Los Angeleno. I use seasonal whole foods to create unique and comforting recipes for casual entertaining.

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