This cheesy chicken fajita casserole is a simple dinner recipe loaded with juicy chicken, colorful peppers, and gooey melted cheese. An easy weeknight meal ready in under 30 minutes.

Ingredients

• 1 ½ lbs (680g) boneless skinless chicken breasts, cut into bite-sized strips
• 2 tablespoons olive oil, divided
• 1 large yellow onion, thinly sliced
• 1 red bell pepper, thinly sliced
• 1 green bell pepper, thinly sliced
• 1 orange bell pepper, thinly sliced
• 3 cloves garlic, minced
• 1 packet (1 oz) fajita seasoning mix (or homemade: 1 tsp chili powder, 1 tsp cumin, ½ tsp paprika, ½ tsp garlic powder, ½ tsp onion powder, ¼ tsp cayenne, salt and pepper to taste)
• 1 cup (240ml) sour cream
• ½ cup (120ml) chicken broth
• 2 cups (226g) shredded Mexican blend cheese (or cheddar/jack mix), divided
• 8 small flour tortillas (6-inch), cut into 1-inch strips
• Optional toppings: fresh cilantro, diced tomatoes, sliced jalapeños, extra sour cream, salsa

Instructions

Step 1

Preheat your oven to 375°F (190°C). While the oven heats, prepare all your ingredients: slice the chicken into uniform bite-sized strips (about ½-inch thick) so they cook evenly. Thinly slice the onions and bell peppers into strips of similar thickness—this ensures they soften at the same rate. Mince the garlic cloves. If using homemade fajita seasoning, combine the spices in a small bowl. Having everything prepped and ready (mise en place) will make the cooking process smooth and quick.

Step 2

Heat 1 tablespoon of olive oil in a large oven-safe skillet (12-inch cast iron or stainless steel) over medium-high heat. Once the oil shimmers, add the chicken strips in a single layer (work in batches if needed to avoid overcrowding—crowding causes steaming instead of browning). Cook without moving for 3-4 minutes until the underside is golden brown and releases easily from the pan. Flip and cook another 2-3 minutes until cooked through (internal temperature 165°F). The chicken should have a nice sear on the outside while staying juicy inside. Transfer the cooked chicken to a plate and set aside.

Step 3

Reduce the heat to medium and add the remaining 1 tablespoon of olive oil to the same skillet. Add the sliced onions and bell peppers. Cook, stirring occasionally, for 5-7 minutes until the vegetables have softened and started to caramelize. The onions should become translucent and the peppers will develop slight char marks—this adds deep flavor. Add the minced garlic and cook for 30 seconds until fragrant, stirring constantly to prevent burning.

Step 4

Return the cooked chicken to the skillet with the vegetables. Sprinkle the fajita seasoning over the mixture and stir well to coat everything evenly. Cook for 1 minute to bloom the spices, which enhances their flavor. Pour in the sour cream and chicken broth, stirring to combine. Let the mixture simmer for 2-3 minutes until the sauce thickens slightly. The sour cream adds a tangy creaminess that balances the spices.

Step 5

Remove the skillet from heat. Stir in 1 cup of the shredded cheese until melted and incorporated. Gently fold in the tortilla strips, making sure they are evenly distributed and coated with the sauce. The tortilla strips will absorb some of the liquid and become tender as they bake, creating a casserole-like texture. Top with the remaining 1 cup of cheese, spreading it evenly over the surface.

Step 6

Transfer the skillet to the preheated oven and bake for 12-15 minutes, until the cheese is bubbly and golden brown on top. If you prefer a browner crust, you can switch to broil for the last 1-2 minutes—watch closely to avoid burning. Let the casserole rest for 5 minutes before serving. This allows the sauce to set slightly and makes serving easier. Garnish with fresh cilantro, diced tomatoes, or a dollop of sour cream if desired.

For best results

• For the juiciest chicken, avoid overcooking. Use an instant-read thermometer to check for 165°F. Cutting the chicken into uniform strips ensures even cooking. If you have time, marinate the chicken in a little lime juice and olive oil for 30 minutes before cooking—it adds brightness and tenderness.
• To make this casserole even more convenient, you can prep the vegetables and chicken ahead of time. Store them in separate airtight containers in the refrigerator for up to 2 days. When ready to cook, simply follow the recipe—the prep time will be cut in half.
• The type of cheese matters. Mexican blend cheese melts beautifully and has a mild flavor that complements the fajita spices. For a sharper taste, use extra-sharp cheddar. If you want a smoky note, try adding a handful of smoked gouda or pepper jack for heat. Always shred your own cheese from a block—pre-shredded cheese contains anti-caking agents that prevent smooth melting.
• Leftovers can be stored in an airtight container in the refrigerator for up to 3 days. To reheat, place in a 350°F oven for 10-15 minutes or microwave in 30-second bursts. The tortilla strips will soften further, but the dish will still be delicious. You can also freeze the unbaked casserole (without the top cheese) for up to 3 months—thaw overnight in the fridge, add cheese, and bake as directed.
• If you want a lower-carb version, skip the tortilla strips and instead add a layer of cauliflower rice or use low-carb tortillas. You can also bulk up the vegetables with zucchini or mushrooms. For a gluten-free option, use corn tortillas or certified gluten-free flour tortillas. The recipe is naturally nut-free and can be made dairy-free by using dairy-free sour cream and cheese alternatives.

Variations

• Make it a chicken steak fajita casserole: Substitute the chicken strips with thinly sliced flank steak or skirt steak. Cook the steak quickly over high heat to medium-rare, then slice against the grain. Follow the same steps—the beef pairs wonderfully with the peppers and cheese. For a smoky twist, use chipotle seasoning instead of traditional fajita mix.
• Turn it into a breakfast casserole: Omit the tortilla strips and add 6 beaten eggs mixed with ¼ cup milk. Pour the egg mixture over the chicken and vegetables before adding the cheese. Bake at 350°F for 20-25 minutes until the eggs are set. Top with cheese and broil for a minute. Serve with salsa and avocado for a hearty morning meal.
• For a vegetarian version, replace the chicken with 2 cans of black beans (rinsed and drained) and 1 cup of corn kernels. Add them along with the vegetables in step 3. The beans provide protein and fiber, while the corn adds sweetness and texture. You can also add roasted sweet potatoes or butternut squash for extra heartiness.

Nutrition

• Calories385 kcal
• Total Fat22g
• Saturated Fat11g
• Cholesterol95mg
• Sodium820mg
• Total Carbohydrates22g
• Dietary Fiber3g
• Sugars5g
• Protein28g

Common Questions