1-First Step: Prepare Your Enchilada Sauce
If you’re making homemade enchilada sauce, start by preparing it first so it can simmer while you work on other components. For an authentic flavor experience, consider trying a traditional red enchilada sauce recipe. If using store-bought sauce, have it measured and ready to use. This step is crucial as the sauce forms the flavor foundation of your vegetable enchilada casserole.

2-Second Step: Sauté Your Vegetables
Heat olive oil in a large pan over medium-high heat. Add the diced white onion, red bell pepper, and jalapeño pepper to the pan. Sauté these vegetables for 6 7 minutes until they begin to soften and develop a slight golden color. This process releases their natural sugars and deepens the flavor profile of your Mexican zucchini casserole.
Next, add the minced garlic to the pan and continue sautéing for 1 2 minutes until fragrant. Be careful not to burn the garlic, as it can become bitter. Once fragrant, turn off the heat and set the pan aside. The aromatic combination of these sautéed vegetables will create a delicious base for your zucchini black bean enchilada casserole.

3-Third Step: Mix the Filling
With your heat off, add the optional cooked rice, quinoa, or farro to the pan with the sautéed vegetables. Next, incorporate the cooked chicken (or alternative protein), rinsed and drained beans, and whole kernel corn. Pour in 1.5 cups of your enchilada sauce and toss everything together until well combined.
This is the perfect time to taste your filling and adjust seasonings if needed. The mixture should be flavorful but not overwhelming, as the cheese and remaining sauce will add more depth. For those looking to make this strictly a vegetarian zucchini enchilada casserole, simply omit the protein or substitute with plant-based alternatives.

4-Fourth Step: Prepare Your Baking Dish
Preheat your oven to 350°F (175°C). While the oven heats, prepare a 9×13-inch baking dish by coating it with cooking spray to prevent sticking. Spread 1/4 cup of enchilada sauce evenly across the bottom of the dish, creating a thin layer that will prevent the zucchini from sticking and add flavor to the bottom of your zucchini enchilada casserole.
Take your thinly sliced zucchini and arrange the slices in an overlapping pattern to completely cover the bottom of the dish. For best results, slice your zucchini uniformly at about 1/8-inch thickness using a mandoline slicer or sharp knife. Pat the zucchini slices dry with paper towels before layering to remove excess moisture, which can make your casserole watery.

5-Fifth Step: Layer Your Casserole
Begin layering your easy zucchini enchilada casserole by spreading half of the filling mixture evenly over the first zucchini layer. Sprinkle 1 cup of shredded cheese over the filling, creating a delicious melty layer that will bind everything together.
Create another zucchini layer on top of the cheese, again overlapping the slices for complete coverage. Add the remaining filling followed by another cup of cheese. Finish with a final layer of zucchini slices and drizzle the remaining 1/4 cup of enchilada sauce over the top. This layering technique ensures that every bite of your low carb zucchini enchilada bake contains a perfect balance of all components.
Gently press each layer down before adding the next to prevent gaps and ensure even cooking. This simple step makes a big difference in the final texture of your dish.

6-Sixth Step: Bake to Perfection
Place your zucchini enchilada casserole in the preheated oven and bake uncovered for 20 minutes. This initial baking time allows the flavors to meld and the zucchini to tenderize. After 20 minutes, remove the pan from the oven and sprinkle the remaining 1 cup of cheese evenly over the top.
Return the dish to the oven and bake for an additional 10 minutes until the cheese is golden and bubbly. The perfect zucchini enchilada casserole should have a slightly crispy top with tender layers underneath.

7-Final Step: Rest and Serve
Once baked, transfer the casserole to a wire rack and let it rest for at least 10 minutes. This resting period is essential as it allows the layers to set, making it easier to cut clean portions. If you slice into it immediately, the layers may slide apart and become messy.
After resting, add your favorite toppings such as chopped cilantro, diced red onion, sliced jalapeños, green onions, Mexican crema, avocado, black olives, or pico de gallo. Slice into portions and serve warm. This healthy zucchini enchilada casserole pairs beautifully with a simple side salad or Mexican-style rice for a complete, satisfying meal that your family will request again and again.