Southwestern Casserole (Vegetarian)

Name: Vegetarian Southwestern Casserole
Prep time: 75 min
Cook time: 20 min
Total time: 110 min
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 jalapeño 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); 1¾ cup cooked black beans, ((from scratch or a can -- drain if from a can)); 1¾ cup Cheddar cheese (white or orange), (grated, divided); 1 cup Pepper Jack cheese, (grated, divided); salt and freshly ground black pepper; about 1 cup loosely packed cilantro leaves, (washed and dried); about ½ large avocado, (thinly sliced); about 2 tablespoons thinly sliced jalapeño pepper, (washed and dried)

May 11, 2022 By valentina 37 Comments

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

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, sautéed, and so on.

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

Ingredients in Vegetarian Southwestern Casserole

zucchini
mushrooms
black beans
onion
garlic
jalapeño
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 ¼ inch thick. (The easiest way to do this is to use a mandoline. If you don’t have one, use a Chef’s knife.)

– 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.

– In a small bowl, combine jalapeño, garlic, chipotles in adobo sauce and cumin. (It’s this, the beans and garnishes that really give this Southwestern Casserole its Latin vibe.)

– Add the onion to a large sauté 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.

– Turn the heat up and add half of the mushrooms. Stirring often, sauté 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.

– Assemble all of the prepared ingredients into a 9 x 13 x 2 inch baking dish as follows: ⅓ of the onion-mushroom mixture, grilled zucchini, ½ cup of the Cheddar and ¼ cup of the Pepper Jack cheese. Repeat this layering process twice more — however, the top layer of cheese will be ¾ cup of the Cheddar and ½ cup of the Pepper Jack.

– Place the baking dish in a preheated 375°F oven and bake for 20 minutes. Remove from the oven, cool a bit, and then garnish with cilantro, avocado and jalapeño slices.

(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, sauté the zucchini in a cast iron skillet and it will acquire a lovely caramelization which also adds delicious flavor.
Avocado, cilantro and jalapeño 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 jalapeño seeds.

Can you make it ahead?

Yes! There are a couple options:

You can grill the zucchini and sauté 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:

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

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

Calories 349 kcal

Equipment

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 jalapeño 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
1¾ cup cooked black beans, (from scratch or a can -- drain if from a can)
1¾ 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 ½ large avocado, thinly sliced
about 2 tablespoons thinly sliced jalapeño pepper, washed and dried

Instructions

Prepare the zucchini: Slice about ½ inch off the ends off of the zucchini and then slice them thinly, about ¼ 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 — 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 375°F.
Prepare the seasonings: In a small bowl, combine the jalapeño, garlic, chipotles in adobo sauce, and cumin. Set aside.
Sauté the vegetables: Coat a large sauté 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, sauté until they’ve shrunk and softened, about 5 minutes. Add the second half of the mushrooms and continue to sauté 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 ⅓ of the mushroom-bean mixture. Sprinkle with ½ cup of the Cheddar and ¼ cup of the Pepper Jack cheese. Repeat this layering process twice more — however, the top layer of cheese will be ¾ cup of the Cheddar and ½ cup of the Pepper Jack.
Bake: Place the baking dish on a sheet pan and place in the preheated 375°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 jalapeño slices.
Serve!

Notes

Calorie count is only an estimate.

Keywords grilled vegetables, Mexican dinner recipes, vegetarian comfort foods

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