Creamy Pepper Jack Chicken Spaghetti Bake

Quick Recipe Version (TL;DR)

• Yield: 6 servings
• Prep Time: 25 minutes
• Cook Time: 35 minutes
• Total Time: 1 hour

Quick Ingredients

• 12 oz dry spaghetti
• 1 1/4 lb boneless, skinless chicken breasts, cut into 1/2-inch pieces
• 2 tbsp olive oil, divided
• 1 small yellow onion, diced
• 1 red bell pepper, diced
• 1 green bell pepper, diced
• 3 cloves garlic, minced
• 1 (14.5 oz) can diced tomatoes, drained
• 2 tbsp unsalted butter
• 2 tbsp all-purpose flour
• 2 1/2 cups whole milk
• 1 cup low-sodium chicken broth
• 8 oz pepper jack cheese, shredded (about 2 cups), divided
• 1 cup shredded mozzarella cheese
• 1 tsp kosher salt, divided, plus more for pasta water
• 1/2 tsp freshly ground black pepper, divided
• 1/2 tsp smoked paprika
• 1/2 tsp chili powder
• 1/4 tsp garlic powder
• 1/4 tsp red pepper flakes (optional, for extra heat)
• 2 tbsp chopped fresh parsley or cilantro, for garnish
• Nonstick cooking spray or a little butter, for greasing the pan

Do This

• 1. Heat oven to 375°F (190°C). Grease a 9×13-inch baking dish. Boil spaghetti in salted water until just shy of al dente; drain.
• 2. Season chicken with 1/2 tsp salt, 1/4 tsp pepper, and garlic powder. Brown in 1 tbsp oil over medium-high heat until cooked through; set aside.
• 3. In remaining 1 tbsp oil, sauté onion and bell peppers until softened; add garlic and cook 30 seconds.
• 4. In the same pot, melt butter, whisk in flour, and cook 1 minute. Slowly whisk in milk and broth; add remaining salt, pepper, paprika, chili powder, and red pepper flakes. Simmer until thickened.
• 5. Off heat, stir in 1 1/2 cups pepper jack until melted. Add cooked spaghetti, chicken, veggies, and drained tomatoes; toss to coat.
• 6. Transfer to baking dish. Top with remaining 1/2 cup pepper jack and mozzarella. Bake 20–25 minutes until bubbly and lightly browned.
• 7. Rest 5–10 minutes before serving. Garnish with chopped parsley or cilantro.

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Why You’ll Love This Recipe

• Creamy, cheesy comfort food with a spicy kick from pepper jack and warm chili spices.
• Great way to stretch a few chicken breasts into a hearty, family-friendly meal.
• One 9×13-inch pan feeds a crowd and reheats beautifully for leftovers.
• Flexible recipe: adjust the heat level, swap veggies, or use rotisserie chicken if you are short on time.

Grocery List

• Produce: 1 small yellow onion, 1 red bell pepper, 1 green bell pepper, 3 cloves garlic, fresh parsley or cilantro
• Dairy: Whole milk, unsalted butter, pepper jack cheese block (or pre-shredded), mozzarella cheese
• Pantry: Dry spaghetti, boneless skinless chicken breasts, olive oil, all-purpose flour, canned diced tomatoes, low-sodium chicken broth, kosher salt, black pepper, smoked paprika, chili powder, garlic powder, red pepper flakes (optional), nonstick spray or extra butter for greasing

Full Ingredients

Pasta and Chicken

• 12 oz dry spaghetti
• 1 1/4 lb boneless, skinless chicken breasts, trimmed and cut into 1/2-inch bite-size pieces
• 1/2 tsp kosher salt
• 1/4 tsp freshly ground black pepper
• 1/4 tsp garlic powder
• 1 tbsp olive oil (for cooking the chicken)

Vegetables and Aromatics

• 1 tbsp olive oil (for sautéing)
• 1 small yellow onion, diced
• 1 red bell pepper, seeded and diced
• 1 green bell pepper, seeded and diced
• 3 cloves garlic, minced
• 1 (14.5 oz) can diced tomatoes, well drained

Creamy Pepper Jack Sauce

• 2 tbsp unsalted butter
• 2 tbsp all-purpose flour
• 2 1/2 cups whole milk, at room temperature if possible
• 1 cup low-sodium chicken broth
• 1/2 tsp kosher salt
• 1/4 tsp freshly ground black pepper
• 1/2 tsp smoked paprika
• 1/2 tsp chili powder
• 1/4 tsp red pepper flakes (optional, for extra heat)
• 6 oz pepper jack cheese, shredded (about 1 1/2 cups), for the sauce

Cheesy Topping and Garnish

• 2 oz pepper jack cheese, shredded (about 1/2 cup), for topping
• 1 cup shredded mozzarella cheese
• 2 tbsp chopped fresh parsley or cilantro, for garnish
• Nonstick cooking spray or a little butter, for greasing the baking dish

Step-by-Step Instructions

Step 1: Prep the oven, pan, and pasta

Preheat your oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish with nonstick spray or a thin layer of butter and set it aside.

Bring a large pot of well-salted water to a boil. Add the spaghetti and cook until just shy of al dente, usually 1–2 minutes less than the package directions. The pasta will continue to cook in the oven, so keeping it slightly under is important to prevent mushiness.

Once cooked, drain the spaghetti and toss it with a drizzle of olive oil (optional) to keep it from sticking. Set aside while you prepare the chicken and sauce.

Step 2: Season and brown the chicken

Pat the chicken pieces dry with paper towels. In a medium bowl, toss the chicken with 1/2 teaspoon kosher salt, 1/4 teaspoon black pepper, and 1/4 teaspoon garlic powder until evenly coated.

Heat 1 tablespoon olive oil in a large deep skillet or the same pasta pot (wiped dry) over medium-high heat. Add the seasoned chicken in a single layer. Cook for 5–7 minutes, stirring occasionally, until the pieces are golden in spots and cooked through with no pink in the center.

Transfer the cooked chicken to a plate or bowl and set aside. Do not wipe out the pan; those browned bits will add flavor to the vegetables and sauce.

Step 3: Sauté the onion, peppers, and garlic

In the same pan, add the remaining 1 tablespoon olive oil. Reduce the heat to medium. Add the diced onion, red bell pepper, and green bell pepper. Cook, stirring often, for 5–7 minutes until the vegetables are softened and the onion is translucent.

Add the minced garlic and cook for 30 seconds until fragrant, being careful not to let it brown. Stir in the drained diced tomatoes and cook for 1–2 minutes to warm through and let some of the excess moisture evaporate.

Transfer the vegetable mixture to the bowl with the cooked chicken or to a separate bowl, and set aside while you make the sauce.

Step 4: Make the creamy pepper jack cheese sauce

In the same pan, melt 2 tablespoons butter over medium heat. Sprinkle in the 2 tablespoons flour and whisk continuously for about 1 minute to form a smooth paste (roux). It should bubble gently but not brown deeply.

Gradually pour in the 2 1/2 cups milk while whisking constantly to prevent lumps. Once the milk is incorporated, whisk in the 1 cup chicken broth. Continue whisking until the mixture is smooth.

Stir in 1/2 teaspoon kosher salt, 1/4 teaspoon black pepper, 1/2 teaspoon smoked paprika, 1/2 teaspoon chili powder, and the optional 1/4 teaspoon red pepper flakes if you like more heat. Bring the sauce to a gentle simmer and cook for 4–6 minutes, whisking frequently, until it thickens enough to coat the back of a spoon.

Turn off the heat. Add 6 oz (about 1 1/2 cups) shredded pepper jack cheese to the hot sauce, a handful at a time, whisking until melted and smooth before adding more. Taste and adjust seasoning if needed.

Step 5: Combine pasta, chicken, veggies, and sauce

Add the drained spaghetti to the pot of cheese sauce. Use tongs or a large spoon to toss until the pasta is well coated. Gently fold in the cooked chicken, the sautéed onion and peppers, and the drained diced tomatoes if they are not already mixed in.

Stir until everything is evenly distributed and all the spaghetti is coated in the creamy pepper jack sauce, with bits of chicken, tomatoes, and peppers tucked throughout. If the mixture seems very thick, you can loosen it with a splash of milk or broth (a tablespoon at a time) until it is creamy but not soupy.

Step 6: Transfer to baking dish and add cheesy topping

Pour the creamy chicken spaghetti mixture into the prepared 9×13-inch baking dish, spreading it into an even layer and making sure the chicken and vegetables are evenly dispersed.

Sprinkle the remaining 2 oz (about 1/2 cup) pepper jack cheese and the 1 cup shredded mozzarella evenly over the top. This duo gives you both flavor and beautiful stretchiness.

Step 7: Bake until bubbly, then rest and garnish

Place the baking dish in the preheated 375°F (190°C) oven. Bake for 20–25 minutes, or until the sauce is bubbling around the edges and the cheese on top is melted and lightly golden in spots.

If you like a deeper golden crust, you can broil on high for 1–2 minutes at the end, watching closely so it does not burn.

Remove the dish from the oven and let it rest for 5–10 minutes. This helps the bake set slightly so it slices more neatly. Just before serving, sprinkle with chopped fresh parsley or cilantro for a pop of color and freshness. Serve warm.

Pro Tips

• Undercook the pasta slightly. Stop boiling the spaghetti 1–2 minutes before al dente. It finishes cooking in the oven and stays pleasantly firm instead of turning mushy.
• Shred your own cheese if possible. Blocks of pepper jack and mozzarella melt more smoothly than pre-shredded, which often contains anti-caking agents.
• Control the heat level. For a milder dish, skip the red pepper flakes and use a milder pepper jack. For more heat, add extra pepper jack and a pinch more chili powder.
• Use the same pot for fewer dishes. Cook the pasta, brown the chicken, sauté the veggies, and make the sauce all in one large pot or Dutch oven before transferring to the baking dish.
• Let it rest before serving. A brief rest after baking lets the sauce thicken slightly so each scoop holds together with lovely creamy strands of spaghetti.

Variations

• Rotisserie chicken shortcut: Swap the raw chicken for 3 cups shredded rotisserie chicken. Skip step 2; simply warm the chicken briefly with the veggies or fold it in when combining everything with the sauce.
• Veggie-packed version: Add 1 cup sliced mushrooms or 1 cup small broccoli florets when sautéing the peppers. Cook until just tender before proceeding.
• Different pasta shapes: Use penne, fusilli, or rigatoni instead of spaghetti. Keep the total dry pasta around 12 oz and cook until just shy of al dente.

Storage & Make-Ahead

Cool leftovers to room temperature, then cover tightly or transfer to airtight containers. Refrigerate for up to 3–4 days. Reheat individual portions in the microwave with a splash of milk or broth to loosen the sauce, or cover the whole dish with foil and warm in a 350°F (175°C) oven for 20–25 minutes until hot throughout.

To make ahead, assemble the unbaked casserole, cover tightly, and refrigerate for up to 24 hours. When ready to bake, let it sit at room temperature for 20–30 minutes while the oven preheats, then bake at 375°F (190°C), adding 5–10 extra minutes if needed until hot and bubbly.

This dish also freezes well. Wrap the unbaked casserole tightly in two layers of foil and freeze for up to 2 months. Thaw overnight in the refrigerator before baking, or bake from frozen at 350°F (175°C), covered, for 45–60 minutes, removing the foil for the last 10–15 minutes to brown the top.

Nutrition (per serving)

Approximate values per serving (1/6 of the recipe): about 700 calories, 39 g protein, 45 g carbohydrates, 37 g fat, 20 g saturated fat, 2–3 g fiber, and 950 mg sodium. Actual numbers will vary based on the specific brands of ingredients you use and any substitutions.