Cheesy Chicken Spaghetti Bake

I am starting to ease back into cozy fall meals, and I could not be more excited. We have a few cooler days in the 70s coming up, which always makes me want to turn on the oven and make something warm and comforting. This Cheesy Chicken Spaghetti Bake is the perfect recipe for that transition from summer into fall.

As the name suggests, this casserole brings together three dependable favorites: chicken, cheese, and spaghetti. It is hearty, creamy, and baked until hot and bubbly, making it a great choice for family dinners or any night when you are craving classic comfort food.

The sauce starts with a basic white sauce, also known as a béchamel. Instead of using only milk, this version is made with chicken broth and cream for extra flavor and richness. Parmesan and sharp cheddar are then stirred into the sauce, turning it into a smooth, savory cheese sauce that coats every strand of pasta.

The casserole is filled with spaghetti, cooked chicken, bell pepper, onion, tomatoes, Italian seasoning, and green chiles. Each ingredient adds color, texture, and flavor, while the creamy cheese sauce ties everything together.

Once the mixture is combined, spread it into a baking dish, top it with even more cheese, and bake until the center is hot and the top is melted and golden. The result is a rich, satisfying casserole that feels just right for cooler evenings.

I have a feeling this Cheesy Chicken Spaghetti Bake will become one of those recipes you return to year after year. It is comforting, family-friendly, and easy to make with simple ingredients, so give it a try the next time you need a cozy dinner.

Ingredients for Cheesy Chicken Spaghetti

• SPAGHETTI – Cooked spaghetti forms the base of the casserole. Cook it just until al dente, so it does not become too soft while baking in the cheese sauce.
• COOKED CHICKEN – Shredded or diced chicken adds protein and makes the casserole hearty enough for a complete meal. Rotisserie chicken is a convenient shortcut.
• ONION – Chopped onion adds savory flavor and a little natural sweetness. Cooking it before assembling the casserole helps soften its texture.
• GARLIC – Minced garlic adds warm, savory flavor that complements the chicken, cheese, and Italian seasoning.
• GREEN BELL PEPPER – Green bell pepper adds color, freshness, and a slightly crisp texture. Chop it into small pieces so it blends evenly throughout the casserole.
• ITALIAN SEASONING – Italian seasoning adds a blend of herbs such as basil, oregano, thyme, and rosemary. It gives it extra flavor without requiring several separate spices.
• BUTTER – Butter creates the base of the roux used to thicken the sauce. It also adds richness and flavor.
• FLOUR – Flour combines with the butter to form a roux. This thickens the chicken broth and cream into a smooth, creamy sauce.
• CHICKEN BROTH – Chicken broth adds savory flavor and provides part of the liquid for the cheese sauce. It gives the casserole more depth than using milk alone.
• LIGHT CREAM – Light cream makes the sauce rich, smooth, and creamy. Half-and-half can usually be used as a substitute.
• DICED TOMATOES – Drained diced tomatoes add color, acidity, and freshness. Tomatoes with green chiles (like Rotel tomatoes)can be used for extra flavor and a mild kick.
• SALT AND PEPPER – Salt brings out the flavors of the chicken, vegetables, and cheese, while black pepper adds mild warmth.
• PARMESAN CHEESE – Parmesan adds salty, nutty flavor to the sauce. It also helps create a richer, more savory cheese mixture.
• SHARP CHEDDAR CHEESE – Sharp cheddar provides bold cheese flavor and a creamy melt. Part is stirred into the sauce, while the remaining cheese is sprinkled over the top before baking.

Instructions for Cheesy Chicken Spaghetti

Preheat the oven to 375°F. Lightly coat a 9 x 13-inch baking dish with nonstick cooking spray.

Bring a large pot of salted water to a boil and cook the spaghetti according to the package directions until al dente. Drain well and set aside.

In the same pot, melt the butter over medium heat. Add the chopped onion, minced garlic, and green bell pepper. Cook for several minutes, stirring occasionally, until the vegetables are tender.

Sprinkle the flour and Italian seasoning over the vegetables. Stir constantly and cook for 1–2 minutes to remove the raw flour taste.

Gradually whisk in the chicken broth and light cream, adding a little at a time so the sauce stays smooth. Continue cooking, stirring frequently, until the mixture thickens and begins to bubble.

Remove the pot from the heat. Stir in the Parmesan cheese and 1 cup of the shredded cheddar until the cheese is completely melted and the sauce is smooth. Season with salt and pepper to taste.

Add the cooked spaghetti, chicken, and well-drained diced tomatoes to the cheese sauce. Gently stir until everything is evenly coated and well combined.

Transfer the mixture to the prepared baking dish and spread it into an even layer. Sprinkle the remaining 1 cup of cheddar cheese over the top.

Bake for 25–30 minutes, or until the casserole is hot and bubbly and the cheese on top is fully melted. Let it rest for a few minutes before serving.

Frequently Asked Questions

Can I use rotisserie chicken for this casserole?
Yes. Rotisserie chicken is a convenient shortcut and works especially well in this recipe. Remove the skin, then shred or dice the meat before adding it to the sauce.

Can I use a different type of pasta?
Yes. Linguine, fettuccine, penne, rotini, or another sturdy pasta can replace the spaghetti. Cook it just until al dente, so it does not become too soft while baking.

Why does the flour need to cook before adding the liquid?
Cooking the flour with the butter for 1–2 minutes removes the raw flour taste. It also helps create a smooth, properly thickened cheese sauce.

How do I prevent the cheese sauce from becoming lumpy?
Add the broth and cream gradually while whisking constantly. Make sure each addition is blended in before adding more liquid.

Can I use pre-shredded cheese?
Yes, but cheese shredded from a block usually melts more smoothly. Pre-shredded cheese contains anti-caking ingredients that can make the sauce slightly grainy.

Can I add other vegetables?
Yes. Mushrooms, spinach, peas, broccoli, or additional bell peppers would all work well. Cook firmer vegetables before stirring them into the casserole.

Can I make this casserole ahead of time?
Yes. Assemble it, cover it tightly, and refrigerate it until you are ready to bake. Add a few extra minutes to the baking time if it goes into the oven cold.

What should I do if the sauce is too thick?
Whisk in a small splash of chicken broth, milk, or cream until it reaches a smooth, creamy consistency.

How should I store leftovers?
Store the cooled casserole in an airtight container in the refrigerator. Reheat individual servings in the microwave or cover and warm them in the oven.

What can I serve with this casserole?
Garlic bread, a green salad, roasted vegetables, green beans, or steamed broccoli would all pair well with it.

Tips and Tricks

• Cook the spaghetti just until al dente. The pasta will continue cooking in the oven, so avoid boiling it until completely soft. Slightly firm spaghetti helps keep the finished casserole from becoming mushy.
• Drain the tomatoes thoroughly. Extra liquid from the canned tomatoes can thin the cheese sauce and make the casserole watery. Let them drain well before stirring them into the pasta mixture.
• Add the broth and cream gradually. Whisk in the liquids a little at a time to keep the white sauce smooth and lump-free. Continue stirring until the sauce is thick and bubbly before adding the cheese.
• Use freshly shredded cheese. Cheese grated from a block melts more smoothly than pre-shredded cheese, which often contains anti-caking ingredients. Sharp cheddar and Parmesan give the casserole the best flavor.
• Let the casserole rest before serving. Allow it to sit for about 5–10 minutes after baking. This gives the sauce time to settle and makes the casserole easier to scoop and serve.

For more recipes like this, try:

• Creamy Sun-Dried Tomato Pasta
• Cottage Cheese Fettuccine Alfredo
• Pesto Cream Sauce
• Garlic Chicken Farfalle

This recipe is adapted from Spend with Pennies.