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This Chicken Fajita Casserole is loaded with onions, bell peppers, cheese and fajita seasonings. It’s a mouthwatering meal that’s low-carb and ready in just 30 minutes with easy prep!

A chicken fajita casserole fresh out of the oven with melty cheese

This dish is one of our go-to recipes whenever we get cravings for chicken fajitas. It’s a quick chicken casserole dinner you can make in 30 minutes from start to finish with one pan for easy cleanup.

OK, so it’s more Tex Mex than Mexican, but it’s still loaded with delicious fajita flavors. Plus, it’s low carb and keto-friendly as well as gluten-free! There are only 327 calories and 6 grams of net carbs per serving.

Want to make it ahead for a party or potluck? No problem! It stores well in the fridge or freezer with easy reheating. So let’s get this started!

Ingredients for Chicken Fajita Casserole

Here’s what you’ll need to make it:

Ingredients for fajita casserole
  • Chicken breasts: You can use boneless skinless chicken breasts cut lengthwise, or chicken fillets or cutlets without cutting. Boneless skinless chicken thighs work too.
  • Onion: Yellow onion or white onion, with red onion as a substitute
  • Bell peppers (capsicum): Red, yellow, orange, green or a combination
  • Olive oil: extra virgin olive oil or any similar oil
  • Jack cheese: Shredded Monterrey Jack is best with Cheddar or Havarti as alternatives
  • Cumin powder (ground cumin)
  • Chili powder
  • Garlic powder: Or granulated garlic or minced fresh garlic
  • Paprika: Regular paprika is best, use smoked paprika only in a pinch
  • Salt and pepper
  • Cilantro for garnish

Don’t forget about sour cream and guacamole for serving too.

Golden and bubbly cheese layer in a baking dish

How to Make a Chicken Fajita Casserole

To make it, the key is cutting the chicken into fillet-size pieces. Using whole chicken breasts makes the baking time too long for the other ingredients, while thin strips cook too fast leaving the vegetables crisp. So cut small-to-medium chicken breasts into halves, and large breasts into thirds.

Next, place the chicken pieces in a single layer into a 9×13-inch baking dish. Add the oil, fajita seasoning and vegetables before topping with shredded cheese. Bake at 400°F for 20-25 minutes until golden and bubbly with the internal temp of the chicken pieces reaching 160°F (it’ll rise 5°F more out of the oven).

To make serving easier, you can shred the chicken pieces with two forks. Garnish with some fresh cilantro and serve hot!

Fajita Seasoning

It’s easy to make your own fajita seasoning, and you can store leftovers in a mason jar for future use. If you go with a storebought mix, you may want to reduce the salt in the recipe to compensate.

Serving a fajita casserole out of a baking dish

What to Serve with Chicken Fajita Casserole

You can serve this casserole with sour cream and guacamole as condiments. For low-carb side dishes, think of refried beans, corn salad, corn on the cob, cauliflower rice, or a green salad.

Alternatively, you can scoop the casserole into tortillas or add some Spanish rice on the side. Don’t forget the Margaritas for drinks too!

Is this casserole keto?

Yes, this recipe has just 6 grams of net carbs per serving, making it suitable for a keto diet.

More casserole recipes:

View all Tex Mex recipes

Chicken fajita casserole in a baking dish
5 from 2 votes

Chicken Fajita Casserole

This Chicken Fajita Casserole has onions, bell peppers and fajita seasoning with melted cheese on top. This restaurant-quality dish is full of mouthwatering Mexican flavors, and it's ready in just 30 minutes!
Prep Time: 10 mins
Cook Time: 20 mins
Total Time: 30 mins
Servings: 6 servings


  • 1 ½ pounds boneless skinless chicken breasts, split lengthwise, or chicken thigh (see note)
  • 3 bell peppers, red, yellow or green capsicum, seeded and sliced into strips
  • 1 large yellow onion, or two medium onions (or white onion)
  • 1 tablespoon olive oil
  • 8 oz Jack cheese, shredded, or cheddar or Havarti (2 cups)
  • fresh cilantro, optional garnish

Fajita Seasoning

  • 1 teaspoon cumin powder
  • 2 teaspoon chili powder
  • 1 1/2 teaspoon garlic powder
  • 2 teaspoon paprika
  • salt and pepper, to taste


  • Preheat the oven to 400°F (200°C) with the rack in the lower middle position. Turn on the convection/forced air if available.
  • Grease a 9×13” baking dish with oil and set aside. Arrange the split chicken breasts in a single layer in the prepared baking dish.
    Chicken fillets in a greased baking dish
  • In a small bowl, combine the cumin, chili powder, garlic powder, paprika, salt and pepper. Drizzle oil on top and sprinkle on half the fajita seasoning.
    Fajita seasoning on chicken breasts in a baking dish
  • Add the sliced onions and bell peppers on top of the chicken. Sprinkle the remaining seasoning on top.
    Onions and bell peppers on top of seasoned meat in a baking dish
  • Top with the shredded cheese and then place the casserole in the oven. Bake for 20-25 minutes or until the chicken reaches an internal temperature of 160°F (check by inserting an instant-read thermometer into the middle of a large piece.)
    Chicken fajita casserole with cheese on top ready to go into the oven
  • Garnish with optional cilantro and serve warm.
    Chicken fajita casserole in a baking dish


  • Fajita Seasoning: You’ll need 2 tablespoons of seasoning if using storebought or a premade mix.
  • Baking Time: Will be up to 5 minutes faster with convection turned on and using a glass or ceramic dish.
  • Spicy: To make it spicy, add up to 1 teaspoon of cayenne to the seasonings and/or 1 sliced jalapeño along with the peppers.
  • Make Ahead Tips: You can also make it ahead in the morning, cover with plastic wrap and refrigerate for up to one day before baking (add 10 minutes to baking time in this case). After baking, cool completely, cover with plastic wrap and refrigerate for up to 3 days. You can also freeze individual portions in airtight containers for up to 3 months.
Nutrition Facts
Chicken Fajita Casserole
Amount Per Serving (6 oz)
Calories 327 Calories from Fat 153
% Daily Value*
Fat 17g26%
Saturated Fat 8g40%
Cholesterol 106mg35%
Sodium 350mg15%
Potassium 655mg19%
Carbohydrates 8g3%
Fiber 2g8%
Sugar 4g4%
Protein 35g70%
Vitamin A 2714IU54%
Vitamin C 79mg96%
Calcium 303mg30%
Iron 2mg11%
* Percent Daily Values are based on a 2000 calorie diet.

Please read our nutrition disclaimer.

Author: TipBuzz
Course: Main Course
Cuisine: Tex Mex
Keyword: chicken fajita casserole, fajita casserole
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Chicken Fajita Casserole made with chicken, onions and bell peppers, fajita seasonings and topped with melted cheese. An easy Tex Mex dinner idea that's ready in 30 minutes with mouthwatering Meican fajita flavors! #fajitacasserole #chickenfajitacasserole