Cheesy Baked Turkey Tetrazzini with Spaghetti and Peas

When the foil comes off, the cheese is still pale, but the edges are bubbling under it. That’s when I know this turkey tetrazzini is ready for its final stretch…

By Willow • October 25, 2026 • Reading time: 9 min

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When the foil comes off, the cheese is still pale, but the edges are bubbling under it. That’s when I know this turkey tetrazzini is ready for its final stretch in the oven. The spaghetti is tucked into a creamy cheddar sauce with mushrooms, onion, and peas, then finished with mozzarella and Parmesan. It’s a cozy way to use cooked turkey, and the 9×13-inch dish makes enough to serve eight.

I build the sauce from butter and flour, then whisk in broth and whole milk until it thickens. Sharp cheddar melts into that base off the heat, so the sauce tastes rich without needing cream. Cooking the spaghetti just to al dente matters here, too: it gets another turn in the oven and stays pleasantly tender instead of going soft. The top turns golden while the sauce bubbles around the edges, and every forkful has a little of that cheesy crust.

Why the Sauce Needs to Be Thick Before It Meets the Spaghetti

A baked pasta casserole has to carry its sauce through two stages: first, the noodles get coated in the saucepan; then the whole dish spends time in the oven. If that sauce is still thin when you combine everything, the finished tetrazzini can be loose instead of creamy. Letting the broth and milk simmer until thickened gives the sauce enough body to cling to the spaghetti and turkey.

There’s another reason to stop the pasta at just al dente. Spaghetti that’s already fully soft has little room left to absorb sauce during baking, so it can turn limp by the time the cheese on top is golden. Cook it according to the package directions, drain it well, and stir it into the sauce while everything is ready to be assembled. You want strands coated all over, not sitting in a puddle at the bottom of the dish.

Keep the stages in order: thicken the sauce before adding the cheddar, then take the saucepan off the heat before stirring in the cheese. That gentle finish helps the cheddar blend into the sauce instead of separating. Once the spaghetti, turkey, and peas are coated, the casserole has what it needs to bake up creamy beneath its crisp-looking cheese topping.

Which Ingredients Keep This Tetrazzini Creamy Without Cream

• Spaghetti — Its long strands catch the sauce and make each serving easy to scoop. Linguine is a straightforward swap if that’s what you have; cook it just to al dente, since the oven softens it further.
• Cremini mushrooms — They bring a savory, earthy note to the sauce. White button mushrooms work in their place, though the flavor will be a little milder. Slice them evenly so they soften at the same pace as the onion.
• Whole milk and low-sodium chicken broth — Together they give the sauce a creamy texture without making it heavy. Whole milk gives a fuller body than lower-fat milk, while low-sodium broth leaves room for the cheese and seasoning without making the sauce too salty.
• Sharp cheddar — This is the cheese that flavors the sauce, so its tang makes a difference. Mild cheddar will melt into the sauce but tastes less pronounced; the sharp variety gives the pasta more character.
• Cooked turkey and frozen peas — Chopped cooked turkey makes this a practical way to use leftovers, and either light or dark meat works. Frozen peas can go straight into the sauce without thawing; they add little sweet pops of flavor without another pan to wash.
• Mozzarella and Parmesan — Mozzarella melts into a stretchy top layer, while finely grated Parmesan adds a salty, savory finish. Keep both for the contrast; using only mozzarella makes the topping milder, and using only Parmesan gives you less of that soft melted layer.

The Order That Keeps the Sauce Smooth and the Top Golden

Cook the Spaghetti to Just Al Dente

Bring a large pot of water to a boil, add the spaghetti and the tablespoon of kosher salt, and cook the pasta according to its package directions until just al dente. Drain it well so excess water doesn’t thin the sauce. Have the noodles ready to stir in as soon as the sauce is finished; drained pasta left waiting can clump together.

Soften the Mushrooms, Onion, and Garlic

Melt two tablespoons of butter in a 4-quart saucepan over medium heat. Add the sliced mushrooms and finely chopped onion, stirring occasionally for about 6 minutes, until they’ve softened. Stir in the minced garlic and cook for 30 seconds; it should smell fragrant but not take on a dark color.

Thicken the Broth-and-Milk Sauce

Add the remaining butter and stir until it melts, then stir in the flour and cook for 1 minute. Gradually whisk in the broth and milk, keeping the whisk moving so the flour blends smoothly instead of forming lumps. Bring the sauce to a simmer and cook, whisking often, for 4 to 6 minutes, until thickened. Take the pan off the heat before stirring in the cheddar, remaining salt, and black pepper.

Coat, Top, and Bake Until Bubbling

Stir the cooked turkey, frozen peas, and drained spaghetti into the sauce until everything is evenly coated, then transfer it to a greased 9×13-inch baking dish. Scatter the mozzarella and Parmesan evenly across the top. Cover tightly with foil and bake at 350°F for 20 minutes, then uncover and bake for 10 to 15 minutes more. Look for bubbling around the edges, a golden top, and 165°F in the center; let the dish rest for 10 minutes before serving.

Two Swaps That Keep the Casserole Familiar

Questions That Come Up Before This Turkey Casserole Goes in the Oven

Cheesy Baked Turkey Tetrazzini with Spaghetti and Peas

Cheesy baked turkey tetrazzini combines spaghetti, chopped turkey, and peas in a creamy cheddar sauce. Baked under mozzarella and Parmesan until golden and bubbling, it makes a hearty casserole with a crisp, cheesy top.

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Prep Time 20 minutes mins

Cook Time 55 minutes mins

resting 10 minutes mins

Total Time 1 hour hr 25 minutes mins

Servings: 8 servings

Course: Dinner

Cuisine: American

Calories: 480

Ingredients Equipment Method Notes

Ingredients

  

For the pasta and dish

• nonstick cooking spray as needed
• 1 package (12 oz) spaghetti
• 1 tbsp kosher salt divided
• 0.5 tsp kosher salt divided

For the sauce

• 2 tbsp unsalted butter divided
• 3 tbsp unsalted butter remaining, divided
• 8 oz cremini mushrooms sliced
• 1 yellow onion small, finely chopped
• 2 cloves garlic minced
• 0.33 cup all-purpose flour
• 2 cups low-sodium chicken broth
• 2 cups whole milk
• 1 cup sharp cheddar cheese shredded
• 0.5 tsp black pepper freshly ground

For the filling

• 3 cups cooked turkey chopped
• 1 cup frozen peas

For the topping

• 1 cup mozzarella cheese shredded
• 0.5 cup Parmesan cheese finely grated

Equipment

• 1 9x13-inch baking dish

Method

 

Prepare and cook the pasta

1. Preheat the oven to 350°F.
2. Coat a 9x13-inch baking dish with nonstick cooking spray.
3. Bring a large pot of water to a boil, add the spaghetti and 1 tablespoon kosher salt, and cook until just al dente according to the package directions.
4. Drain the spaghetti well.

Make the sauce

1. Melt 2 tablespoons of the butter in a 4-quart saucepan over medium heat.
2. Add the mushrooms and onion and cook, stirring occasionally, until softened, about 6 minutes.
3. Add the garlic and cook for 30 seconds.
4. Add the remaining 3 tablespoons butter and stir until melted.
5. Stir in the flour and cook for 1 minute.
6. Gradually whisk in the broth and milk and bring to a simmer.
7. Cook, whisking often, until thickened, 4 to 6 minutes.
8. Remove from the heat and stir in the cheddar, remaining 1/2 teaspoon salt, and black pepper.

Assemble and bake

1. Stir the turkey, peas, and drained spaghetti into the sauce until evenly coated.
2. Transfer the mixture to the prepared baking dish.
3. Sprinkle the mozzarella and Parmesan evenly over the top.
4. Cover the dish tightly with foil and bake for 20 minutes.
5. Uncover and bake for 10 to 15 minutes, until bubbling at the edges, golden on top, and 165°F in the center.
6. Let the tetrazzini rest for 10 minutes before serving.

Notes

Cook the spaghetti just until al dente so it holds its texture after baking. Refrigerate leftovers for 3 to 4 days; freeze for up to 3 months. For a gluten-free version, use gluten-free spaghetti and a gluten-free all-purpose flour blend.