With a delectable mix of tender dark meat chicken, sweetly caramelized peppers & onions, and a creamy blend of not one but TWO cheeses, this Keto Chicken Fajita Casserole tastes nothing like any diet food we’ve ever tried. 🤷‍♀️ Best of all, this low-carb oven chicken fajita bake is made with fewer than 10 ingredients and only 20 minutes of active prep!

Jump to Recipe

Why We Love This Recipe

While the CCLS kitchen isn’t really focused on recipes that would qualify as “diet food,” some of our longtime favorites just so happen to fit neatly into some of those boxes. Don’t you just love when that happens?!? Us too. 

Whenever we have a loved one who is experimenting with a new eating routine, we always do our best to honor them when they grace our dinner table.

This low-carb chicken fajita casserole recipe is one we turn to again and again, even if keto friends aren’t coming over. Honestly, it’s SO GOOD. Who doesn’t love a pile of creamy, cheesy goodness?!?

Aside from being lick-the-plate-clean tasty, this fajita chicken casserole recipe is also: 

• Quick & Easy – All you need is 20 minutes of prep time in the kitchen, making this a slam-dunk option for busy weeknights. 
• Made With Only 8 Ingredients – Salt and pepper are two of them, so you KNOW it’s simple.
• Super Versatile – There are so many ways to serve this cheesy chicken fajita bake, you’ll find no shortage of fun new ways to keep things fresh and interesting. Read on below for tons of ideas!
• Family-Friendly – Chicken, cheese, and roasted onions & peppers make for a kid-friendly meal that even adults will love.

Ingredients & Substitutions

Making an easy chicken fajita casserole low carb simply requires that you omit any rice or starches. Here’s what we use in our recipe:

• Boneless, Skinless Chicken Thighs – We love chicken thighs because they’re nearly impossible to overcook. When your mind is in a frenzy, having a little extra insurance in the kitchen puts our minds at ease. Feel free to swap in boneless skinless chicken breasts, or use leftover cooked chicken or pulled rotisserie chicken instead.
• Red Bell Pepper – Orange or yellow will work, but the color won’t be quite so vibrant on the plate. You can also *add* green peppers to the mix, but we don’t recommend making a full swap since the red, orange, and yellow varieties are much sweeter.
• Onion – Feel free to use any variety of onion (e.g. yellow, white, red, sweet, or even shallots) that you have on hand.
• Cream Cheese – We like to use full-fat dairy since the low-fat and fat-free versions are often loaded with weird stabilizers and artificial ingredients. If you want to make this keto fajita casserole a little lighter, we suggest using Neufchatel cheese instead.
• Cheddar – Mild, medium, or sharp will all work here, so choose what you like. 
• Fajita Seasoning – We always keep packets of this spice mix in the pantry for a quick flavor booster. Feel free to use taco seasoning instead, or swap in homemade fajita seasoning mix. 
• Salt & Pepper – Simple seasonings that you can add to taste.

How To Make Keto Chicken Fajita Casserole

You’re going to LOVE how quickly this chicken fajita meal comes together. Here’s how it’s done:

Step 1: Cook Chicken. Preheat oven to 350. Put the chicken in the casserole dish you will be using for this dish. Cover with foil and bake until cooked to 160 degrees, about 30-35 min. Cool for a few minutes and then shred or chop into bite-sized pieces. Drain any cooking liquid from the casserole dish.

Step 2: Cook Veggies. While the chicken cooks, cook the pepper and onion in a frying pan coated with cooking spray over medium-low heat until they are golden and soft. Let the onions carmelize as the chicken is cooking in the oven. Keep heat between low and medium and stir every 5-10 min. Cool until warm.

Step 3: Assemble. In a large bowl mix the cream cheese, half of the shredded cheddar, and the fajita seasoning. Add the chopped chicken and cooked onion and pepper. Put the mixture back into the same casserole dish you cooked the chicken in. Sprinkle on the remaining cheese.

Step 4: Bake at 350 for 25-30 min until hot and bubbly.

Optional Variations

As much as we love this low-carb fajita casserole just the way it’s written, there’s plenty of room for you to make your own mark on it. Here are a few worthwhile variations to try:

• Extra Rich – You can also cook the veggies in butter if you want to bump up your fat macros. 
• Use White Meat – Lighten things up by swapping in boneless skinless chicken breasts for the thighs.
• Make it Spicy – Add some chopped jalapeño to the peppers during sautéing and use fiery pepper jack cheese in place of the cheddar.
• Swap In Steak – Steak Fajita Casserole is just as delicious as the chicken version! We recommend grilling or pan-frying your steak to perfection, cutting it into slices, and then baking as directed.
• Dairy-Free Fajita Casserole – Use your favorite plant-based cheddar and cream cheese substitutes.

Expert Tips

• Grate your own cheese. As tempting as it is to grab a bag of pre-shredded cheese to cut down on prep time, it’s not worth the 5 minutes of time saved. Pre-shredded cheese is coated in a starchy substance to keep it from glomming together in a blob in the bag, but the starch also prevents it from melting as well as fresh cheese.
• Leftover chicken fajita casserole can be kept in a clean, airtight container in the fridge for up to 5 days. To reheat, use the microwave (better for single servings) or pop the whole casserole in an oven at 300F for about 15 minutes, or until warmed through.

Serving Suggestions

While we love eating this chicken fajita casserole keto-style, there’s more than one way to serve it up. Here are a few of our favorite variations:

• Stuffed Peppers – Add the cheesy fajita mix to hollowed-out bell peppers or poblano peppers for a tasty and colorful low-carb dinner.
• Wraps – Use large pieces of lettuce, cabbage, burrito-sized tortillas, or any other variety of wraps (regular or low-carb) to hold your cheesy chicken dinner.
• Tacos – We like to serve our casserole tucked into warm taco-sized tortillas, then top with sour cream and salsa. They’re delish!
• Rice Bowls – Serve your fajita mix over a bowl of regular, Mexican, or cauliflower rice, then top with your favorite garnishes (e.g. fresh cilantro, salsa, extra cheese, black beans, avocado, etc).
• Nachos – Layer crispy tortilla chips with the unbaked fajita mix and an extra sprinkling of cheese (making sure to work one layer at a time so all the chips get some toppings), then bake in 10-minute intervals until melty and delicious. Top with your favorite nacho fixin’s (e.g. pickled jalapeños or pickled red onions, beans, salsa, cilantro, scallions, etc) and dig in! For a keto version, swap in low-carb chips or use roasted cauliflower florets as your base.
• Pasta – Toss the hot, creamy chicken mixture with your favorite shape of boiled noodles. Swap in heart of palm pasta for a keto-friendly fajita pasta!

FAQs

What’s the difference between taco seasoning and fajita seasoning?

Taco seasoning and fajita seasoning are both spice blends used to add flavor to Mexican-inspired dishes, but they have some differences in terms of their composition and intended use:
1. Taco seasoning typically has a bold and robust flavor with a balance of spices like chili powder, cumin, paprika, garlic powder, onion powder, oregano, and sometimes additional ingredients like red pepper flakes or cayenne pepper. It aims to provide a robust and slightly spicy taste to mimic the flavors of traditional Mexican tacos.
2. Taco seasoning can vary in heat level, depending on the amount and type of chili powder or spices used. It can range from mild to medium spiciness, but it can be adjusted based on personal preference.
3. Taco seasoning is often used in a variety of Mexican-inspired dishes beyond just tacos. It can be added to ground meat, such as beef or chicken, for flavorful fillings, and also used in dishes like enchiladas, quesadillas, or Mexican-inspired casseroles. Fajita seasoning, on the other hand, typically focuses on flavors that complement grilled or sautéed meat, particularly for fajitas. It tends to have a milder and smokier flavor compared to taco seasoning.
4. Fajita seasoning is specifically designed to enhance the flavors of fajitas, which traditionally consist of marinated and grilled meats, such as chicken, beef, or shrimp, along with sautéed onions and bell peppers.

Is fajita seasoning keto?

Fajita seasoning can be keto-friendly depending on the specific ingredients used.
To ensure that your fajita seasoning is keto-friendly, it’s important to check the labels or prepare your own seasoning mix using individual spices. Some store-bought fajita seasoning mixes may contain fillers, anti-caking agents, or added sugars, which can increase the carb content.
If you’re following a strict ketogenic diet, you may want to make your own fajita seasoning at home using individual spices to have better control over the ingredients. This way, you can adjust the flavor and carb content to suit your dietary needs.

What temperature should chicken be cooked to?

165F is considered the minimum safe temperature for chicken.

More Easy Casserole Recipes

• Southern-Style Old-Fashioned Mac and Cheese Casserole
• Easy Keto Jambalaya
• Spaghetti Scampi e Spinaci

If y’all tried this sumptuous recipe for our Keto Chicken Fajita Casserole, holler and let us know how it turned out for you by giving us a ⭐️⭐️⭐️⭐️⭐️ rating and commenting below. You can also always feel free to tag us (@creamcheeseandlemonsqueeze) in your social media posts so we can cheer you on.

Alright, y’all. Thanks so much for stopping by! For even more down-home Mississippi Coastal cooking inspiration, be sure to follow us on Instagram, Pinterest, Facebook, and TikTok. You can also get all of our newest content delivered straight to your inbox by signing up for our weekly newsletter. We can’t wait to see you again soon!

XO,

Anna & Ashley