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This homemade Chicken Spaghetti Casserole is adapted from the Pioneer Woman’s recipe and uses a shredded Costco rotisserie chicken to make it easy to throw together on a weeknight. Perfectly al dente pasta combine with a made-from-scratch cream of mushroom soup sauce with chopped green pepper, pimentos, diced onion, and a generous amount of shredded cheddar cheese. This is a family favorite!

We love a good pasta dinner! Some of our other favorites are Chicken Fettuccine Alfredo, 30 Minute Cajun Pasta with Sausage and Peppers, and Homemade Hamburger Helper Cheeseburger Pasta Skillet (with Video!)

An image of a cheesy, hot, Chicken Spaghetti Casserole made with shredded Costco rotisserie chicken meat.

Chicken Spaghetti

I don’t know where chicken spaghetti came from in the first place, but I know I first saw it in the Pioneer Woman‘s cookbook years ago. This chicken spaghetti casserole recipe, along with her chicken pot pie recipe, were my two favorites from that book.

I love a good casserole, and this isn’t the first spaghetti casserole I’ve posted on the blog. My other favorite is creatively called “spaghetti casserole” but really I think of it as a poor man’s lasagna, made with cottage cheese and spaghetti instead of ricotta and lasagna noodles. Another favorite dinner casserole that you really should try is my cheesy chicken broccoli and rice casserole.

The biggest change I made to the Pioneer Woman’s original chicken spaghetti recipe was to swap out the cream of mushroom soup in favor of a homemade version. It takes very little additional time, tastes WAY better, and is better for you anyway. 

An image of a pile of chicken spaghetti casserole on a plate.

Chicken Spaghetti is one of the best make ahead meals

I love chicken spaghetti casserole because it’s such an easy recipe to make ahead and stick in the fridge or freezer until you need it.

An image of a baking dish of an easy weeknight casserole made with rotisserie chicken, spaghetti, cheese, and homemade cream of mushroom soup.

All it takes is about 15 minutes of chopping veggies, making the mushroom sauce, and mixing the casserole components together, and then it bakes in the oven until hot and bubbly. The beauty of it is that you can make the casserole a day or two in advance and it tastes just as good when you finally decide to bake it as when it was first made.

Chicken spaghetti also makes a great freezer meal! You can freeze this chicken spaghetti recipe for 2 months, then thaw in the fridge overnight. It’s one of those recipes that I keep in my back pocket for taking to friends who have had babies or are dealing with family health issues because it can be ready and on hand whenever they need it. 

It’s honestly not a bad idea to double the recipe and make two casseroles as long as you are making one. Especially since you only need half of a green pepper and half of an onion to make one casserole. Keep one in the freezer to have on hand for a busy weeknight or give one away to a friend in need!

An image of a plate of an easy weeknight pasta dinner with Costco rotisserie chicken, spaghetti noodles, pimentos, green bell pepper, mushrooms, and cheese.

Ingredients in Chicken Spaghetti Casserole

  • cooked chicken
  • spaghetti noodles
  • diced mushrooms
  • flour
  • butter
  • chicken broth
  • milk
  • salt
  • pepper
  • green bell pepper
  • pimentos (a type of jarred pepper that is sweet and mild but 1/2 of a chopped red bell pepper will also work)
  • yellow onion
  • sharp cheddar cheese
An image of a rotisserie chicken, uncooked spaghetti noodles, chopped onion, chopped green bell pepper, diced onions, shredded cheddar cheese, and a jar of pimentos.

How to Make Chicken Spaghetti

  1. Cook some chicken or buy a rotisserie chicken:  I’ve used leftover grilled chicken, roasted chicken, poached chicken, and those rotisserie chickens that we all love. Honestly, I think I prefer the rotisserie chicken in this recipe! It just makes things so much easier and I almost always grab one anytime I’m at Costco anyway since they are so convenient and priced reasonably. Shred or cube the chicken. I usually get around 3 to 4 cups worth off one rotisserie chicken.
  2. Cook the spaghetti:  I took a note from the Pioneer Woman’s book where she cooks her spaghetti noodles in some of the broth that is leftover from cooking a cut-up fryer chicken. Since I use a rotisserie chicken, I usually just add about 3 tablespoons of “Better Than Bouillon” chicken base to the pot of water that I use to boil the spaghetti in. It’s optional and you could just cook the pasta in regular salted water, but I do think it adds flavor.
  3. Make the Cream of Mushroom Soup sauce:  Just melt a little butter in a large pan, then add diced mushrooms and cook until the mushrooms have released most of their liquid, about 5 minutes. Then add a little more butter and sprinkle some flour over the sauteed mushrooms, stirring to cook it for about 30 seconds. Add some liquid in the form of chicken broth and milk and season with salt and pepper, whisking and cooking over a simmer until the sauce thickens, about 5 minutes.
  4. Combine all of the casserole ingredients in a big bowl:  Save about 3/4 cup of shredded cheese to sprinkle over the top, but otherwise, the shredded chicken, cooked and drained spaghetti, and chopped veggies get thrown into a big bowl and stirred together with the homemade cream of mushroom soup. Then transfer it to a large baking dish and sprinkle with the remaining cheese. I find that the pasta will often look a little dry at this point, so I will pour 1 extra up of chicken broth over the casserole once it is in the pan.
  5. Bake for 40 minutes until hot and bubbly!
A collage showing step-by-step images of how to make cream of mushroom soup from scratch.
An image of the ingredients for chicken spaghetti in a bowl.
An image of an unbaked chicken spaghetti casserole before being topped with cheese and baked in the oven.
An image of a cheesy, hot, bubbly chicken spaghetti casserole on a striped napkin.

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An image of a homemade Chicken Spaghetti Casserole topped with melted cheddar cheese.
Yield: 10 servings

Chicken Spaghetti Casserole

This homemade Chicken Spaghetti Casserole is adapted from the Pioneer Woman's recipe and uses a shredded Costco rotisserie chicken to make it easy to throw together on a weeknight.  Perfectly al dente pasta combine with a made-from-scratch cream of mushroom soup sauce with chopped green pepper, pimentos, diced onion, and a generous amount of shredded cheddar cheese.  This is a family favorite!

Prep Time 15 minutes
Cook Time 40 minutes
Total Time 55 minutes

Ingredients

Sauce

  • 4 tablespoons butter, divided
  • 8 ounces cremini mushrooms, diced
  • 3 tablespoons all-purpose flour
  • 2 cups chicken broth
  • 1 cup milk
  • 1/4 teaspoon salt
  • 1/4 teaspoon black pepper

Casserole

  • 1 pound spaghetti, broken into 2-inch pieces
  • 3 tablespoons chicken bouillon
  • 3-4 cups cooked chicken, shredded
  • 1 small yellow onion, chopped
  • 1/2 green bell pepper, chopped
  • 1 (4-ounce) jar pimentos, drained
  • 2 1/2 cups grated cheddar cheese, divided
  • 1 teaspoon seasoned salt
  • 1/8 to 1/4 teaspoon cayenne pepper
  • 1 cup chicken broth

Instructions

  1. Preheat oven to 350 degrees F.
  2. Melt 1 tablespoon of butter in a large sauce pan, then add the diced mushrooms and cook for 3-5 minutes over medium-high heat, stirring frequently, until most of the liquid released from the mushrooms cooks off.
  3. Add remaining butter and let melt, then sprinkle with the flour and stir and cook for 30 seconds.
  4. Whisk in the chicken broth and milk, about 1/2 cup at a time, until combined. Stir in salt and pepper, then simmer for 3-5 minutes until slightly thickened. Remove sauce from heat and set aside.
  5. Fill a large pot with water and bring to a boil. Add the spaghetti and season the water with about 1 tablespoon of salt. I also like to add 3-4 tablespoons of chicken-flavored Better Than Bouillon to the water to flavor the spaghetti noodles while they cook. Cook according to package directions until al dente, then drain.
  6. In a large bowl, combine the cooked spaghetti noodles, chicken, onion, bell pepper, pimentos, 1 3/4 cups cheese, seasoned salt, and cayenne pepper. Pour the sauce over everything and stir to combine. Transfer to a 9x13-inch baking dish.
  7. Pour remaining 1 cup chicken broth over the pasta, then sprinkle with the remaining 3/4 cup cheese. Bake for 35 to 40 minutes until the cheese is melted and the casserole is hot and bubbly.

Notes

I use a rotisserie chicken from Costco that I pull the meat off of and shred, but the Pioneer Woman's original recipe calls for 1 cut-up fryer chicken to be placed in a large pot of water, brought to a boil, then simmered at medium heat until cooked through, about 25 minutes. Really, any cooked chicken would work, included oven roasted chicken breasts, leftover BBQ chicken, etc.

To Freeze: Assemble the casserole, then cover tightly with foil and freeze. Thaw in the fridge overnight when ready to use, then pull out and set on the counter while the oven preheats for about 15 minutes. Bake as directed above until hot all the way through.

Adapted from "The Pioneer Woman Cooks".

Nutrition Information:

Yield:

10

Serving Size:

1
Amount Per Serving: Calories: 620Total Fat: 36gSaturated Fat: 15gTrans Fat: 0gUnsaturated Fat: 18gCholesterol: 196mgSodium: 1265mgCarbohydrates: 20gFiber: 1gSugar: 2gProtein: 50g
© Amy
Cuisine: American / Category: Dinner

Also, be sure to check out these amazing weeknight pasta bakes shared by some of my food blogging friends today! These are perfect for back-to-school!

A collage of weeknight pasta bake casseroles.

Turkey Casserole
Baked Pasta with Sriracha Cream Sauce
Chicken Spaghetti Casserole
Chicken Sausage Pasta Bake
Pepperoni Pizza Pasta Bake
Pizza Pierogi Casserole
Baked Spinach Ravioli Skillet
Fiesta Pasta Bake
Chicken Alfredo Stuffed Shells
Chicken Glorioso Pasta Bake