Chicken Fajita Casserole is a tasty, easy-to-make dish that brings all the zesty flavors of fajitas into one simple bake. You get tender chicken, colorful bell peppers, onions, and melty cheese all mixed together with warm spices. It’s like having a fajita night without the mess of cooking everything on the stove.
I love making this casserole when I need a meal that’s both comforting and quick. It’s one of those recipes where I throw in what I have on hand, and it always turns out great. Plus, it’s perfect for busy weeknights when you want something delicious but don’t want to spend too much time cooking.
My favorite way to serve it is topped with a dollop of sour cream and some fresh avocado slices or salsa on the side. It feels like a little fiesta on the dinner table! This casserole is also great for leftovers — it reheats well and keeps those fajita flavors bright and fresh.
Key Ingredients & Substitutions
Chicken breasts: I recommend thinly sliced boneless, skinless chicken breasts for quick cooking and tenderness. You can swap for thighs if you prefer juicier meat or want a richer flavor.
Bell peppers and onions: These add crunch and color. Feel free to mix different colored peppers or skip the yellow if unavailable. Red, green, and orange all work well.
Fajita seasoning: A store-bought packet is easy, but homemade seasoning gives you control over spices and heat. Adjust cayenne to suit your taste or leave it out for mild flavor.
Cheese: Monterey Jack melts smoothly, and Cheddar adds sharpness. You can use all one type or try a Mexican blend for more variety.
Sour cream and cilantro: These fresh toppings cool down the spices and add brightness. Greek yogurt is a great sour cream substitute.
How Do You Cook the Chicken and Veggies Just Right for the Best Fajita Flavor?
To get tender chicken and perfectly cooked peppers and onions without mushiness:
- First, heat olive oil in your skillet over medium-high heat so it’s hot enough to sizzle.
- Cook the chicken slices seasoned with fajita mix just until they start to turn white – about 5 to 7 minutes.
- Then add your sliced bell peppers and onions; stir often so veggies soften but keep a bit of crunch—about 5 more minutes.
- Make sure chicken is fully cooked through but avoid overcooking, so it stays juicy inside.
- This method seals in fajita flavors and makes your casserole colorful and tasty.
Equipment You’ll Need
- Large oven-safe skillet or cast-iron pan – I love it because it goes from stove to oven easily and keeps everything contained for baking.
- Knife and cutting board – for slicing chicken, peppers, and onions smoothly and safely.
- Measuring spoons and cups – to add accurate amounts of seasonings and cheeses.
- Grater – for shredding cheese quickly and easily.
- Oven mitts – to handle the hot skillet when baking and serving.
Flavor Variations & Add-Ins
- Swap chicken for sliced steak or shrimp for a different protein twist that cooks quickly and adds richness.
- Add sliced jalapeños or a pinch of chipotle powder for extra heat and smoky flavor.
- Mix in roasted corn or black beans to boost the veggie content and add texture.
- Top with sliced avocado or a squeeze of lime for a fresh, tangy note that balances the spicy flavors.
How to Make Chicken Fajita Casserole
Ingredients You’ll Need:
- 1.5 lbs boneless, skinless chicken breasts, thinly sliced
- 1 red bell pepper, thinly sliced
- 1 green bell pepper, thinly sliced
- 1 yellow bell pepper, thinly sliced (optional)
- 1 medium onion, thinly sliced
- 2 tbsp olive oil
- 1 packet (1 oz) fajita seasoning mix or homemade fajita seasoning* (see below)
- 1 cup shredded Monterey Jack cheese
- 1 cup shredded Cheddar cheese
- 1/2 cup sour cream (for topping)
- Fresh cilantro leaves, chopped (for garnish)
- Salt and pepper, to taste
Homemade Fajita Seasoning:
- 1 tsp chili powder
- 1 tsp paprika
- 1/2 tsp garlic powder
- 1/2 tsp onion powder
- 1/2 tsp cumin
- 1/4 tsp oregano
- 1/4 tsp cayenne pepper (optional)
- Salt and pepper to taste
Time Needed
This recipe takes about 15 minutes to prepare and cook the chicken and vegetables on the stove, plus another 10 to 13 minutes baking time in the oven. In total, plan for about 30 minutes from start to finish!
Step-by-Step Instructions:
1. Preheat and Prepare:
Set your oven to 375°F (190°C) to get it ready for baking. Thinly slice your chicken, peppers, and onion while the oven heats.
2. Cook the Chicken:
Warm 2 tablespoons of olive oil in a large oven-safe skillet or cast iron pan over medium-high heat. Add the sliced chicken, sprinkle with your fajita seasoning, and season with salt and pepper. Cook, stirring occasionally, until the chicken is mostly cooked through (about 5–7 minutes).
3. Add the Veggies:
Mix in the sliced onions and bell peppers with the chicken. Continue to cook, stirring every few minutes, until the vegetables are soft but still vibrant and the chicken is fully cooked (around 5 minutes).
4. Add Cheese and Bake:
Spread the chicken and pepper mixture evenly in the skillet. Sprinkle shredded Monterey Jack and Cheddar cheeses across the top. Place the skillet in the oven and bake until the cheese melts and bubbles, about 10 minutes. For a golden, crispy cheese top, broil for 2-3 more minutes, watching closely.
5. Serve and Garnish:
Carefully remove the hot skillet from the oven. Let it cool for a minute, then add a dollop of sour cream on top. Finish with freshly chopped cilantro for a pop of fresh flavor. Serve warm, either by itself or with tortillas, rice, or your favorite Mexican sides.
Can I Use Frozen Chicken for This Casserole?
Yes! Just be sure to thaw the chicken completely before slicing and cooking. Thaw overnight in the fridge or use the cold water method for faster results. This helps ensure even cooking and a tender texture.
Can I Make This Casserole Ahead of Time?
Absolutely! Prepare the chicken and veggies as directed but hold off on adding cheese and baking. Store the mixture in an airtight container in the fridge for up to 24 hours, then add cheese and bake just before serving.
How Should I Store Leftovers?
Keep any leftovers in an airtight container in the refrigerator for up to 3 days. Reheat in the oven or microwave until warmed through. Adding a fresh dollop of sour cream when serving helps refresh the flavors.
What Can I Serve with Chicken Fajita Casserole?
This dish is great on its own or paired with warm tortillas, Mexican rice, or a simple side salad. You can also add guacamole or salsa for extra flavor and texture.
