Leftover Roast Beef and Noodle Casserole

Finding a hearty dinner that satisfies the whole family while using up leftovers can feel like an impossible task. After all, comfort food that actually tastes good is hard to come by when you’re trying to stretch last night’s roast beef, and things get even trickier when you want something that doesn’t require a ton of prep work after a long day.

Thankfully, this roast beef and noodle casserole hits all the right notes: it’s filling and flavorful, easy to throw together on busy weeknights, and perfect for using whatever leftover roast beef and vegetables you have sitting in your fridge.

What Kind of Roast Beef Should I Use?

This casserole is perfect for using up leftover roast beef from Sunday dinner, but you don’t need to limit yourself to just one cut. Whether you have leftover chuck roast, sirloin tip, or even deli roast beef, they’ll all work great in this recipe. The key is cutting your beef into bite-sized cubes so they distribute evenly throughout the casserole and are easy to eat. If your roast beef is on the drier side, don’t worry – the creamy sauce will help moisten it as it bakes. You can even use store-bought deli roast beef if you don’t have leftovers on hand, just make sure to get it sliced thick so you can cube it properly.

Options for Substitutions

This comforting casserole is great for using up leftovers, and you can easily swap ingredients based on what you have:

• Rotini pasta: Any short pasta shape works well here – try penne, fusilli, or even egg noodles. Just cook according to package directions and you’re good to go.
• Leftover roast beef: Don’t have roast beef? Use leftover pot roast, steak, or even rotisserie chicken. You could also brown some ground beef if that’s what you have on hand.
• Condensed mushroom soup: Cream of celery or cream of chicken soup work as substitutes. If you want to skip canned soup altogether, make a simple white sauce with butter, flour, and milk.
• Mozzarella cheese: Cheddar, Swiss, or a blend of cheeses all melt nicely in this casserole. Use whatever cheese your family enjoys most.
• Fresh mushrooms: If you’re not a mushroom fan, try diced bell peppers, celery, or zucchini instead. Frozen mixed vegetables also work well.
• Dijon mustard: Regular yellow mustard or whole grain mustard can replace dijon. Start with half the amount and taste as you go since regular mustard is milder.

Watch Out for These Mistakes While Cooking

The biggest mistake with this casserole is overcooking the pasta during the initial boiling – since it will continue cooking in the oven, undercook your rotini by about 2 minutes so it doesn’t turn mushy in the final dish.

Another common error is not properly thickening your sauce base before combining everything, so make sure to whisk that flour into the beef broth thoroughly and let it simmer until it coats the back of a spoon.

Don’t skip sautéing the carrots and mushrooms beforehand either, as raw vegetables will release too much moisture during baking and make your casserole watery instead of creamy.

Finally, resist the urge to skip the resting period after baking – let the casserole sit for 10 minutes before serving so the sauce can thicken up and everything holds together when you scoop it out.

What to Serve With Roast Beef and Noodle Casserole?

This hearty casserole is pretty much a complete meal on its own, but I love serving it with a simple side salad to balance out all that creamy goodness. A crisp green salad with mixed greens, cherry tomatoes, and a light vinaigrette works perfectly to cut through the richness of the cheese and mushroom flavors. Garlic bread or dinner rolls are also great for soaking up any extra sauce, and they make the meal feel even more cozy and filling. If you want to add some color to your plate, steamed green beans or roasted broccoli pair nicely with the beef and mushroom flavors in the casserole.

Storage Instructions

Refrigerate: This casserole keeps really well in the fridge for up to 4 days when covered tightly with foil or plastic wrap. I actually think it tastes even better the next day because all those flavors have time to meld together. Just make sure to let it cool completely before covering to avoid condensation.

Freeze: You can definitely freeze this casserole for up to 3 months! I like to portion it into individual servings in freezer-safe containers, which makes weeknight dinners so much easier. If you’re freezing the whole casserole, wrap it really well in plastic wrap and then foil to prevent freezer burn.

Reheat: To warm up leftovers, cover with foil and bake at 350°F for about 20-25 minutes until heated through. You can also microwave individual portions for 2-3 minutes, stirring halfway through. If it seems a bit dry after reheating, just add a splash of beef broth to bring back that creamy texture.

Preparation Time	15-20 minutes
Cooking Time	30-35 minutes
Total Time	45-55 minutes
Level of Difficulty	Medium

Estimated Nutrition

Estimated nutrition for the whole recipe (without optional ingredients):

• Calories: 2100-2300
• Protein: 130-150 g
• Fat: 90-100 g
• Carbohydrates: 230-250 g

Ingredients

For the pasta and filling:

• 16 oz rotini noodles
• 2 carrots, sliced
• 2 cups sliced mushrooms
• 2 cups cooked roast beef, cubed
• 2 tsp dried thyme
• 1 tsp kosher salt
• 1/2 tsp coarse ground black pepper
• 1 1/2 cups shredded mozzarella cheese

For the sauce:

• 2 tbsp flour
• 2 cups beef broth
• 20 oz condensed mushroom soup
• 2 tbsp worcestershire sauce
• 1 tbsp dijon mustard

Step 1: Cook the Rotini Noodles

• 16 oz rotini noodles

Preheat your oven to 375°F (190°C).

Bring a large pot of salted water to a boil.

Add the rotini noodles and cook for about 2 minutes less than the package instructions recommend.

Drain the noodles and set them aside.

Undercooking the pasta slightly helps it maintain some texture after baking.

Step 2: Make the Roux and Thicken the Sauce

• 2 tbsp flour
• 2 cups beef broth

In the same pot, melt the butter (you may use about 2 tablespoons) over medium heat.

Add the flour and whisk constantly until the mixture combines and the flour is no longer dry, cooking for about 1 minute.

Gradually pour in the beef broth while whisking to avoid lumps.

Continue to whisk and cook for 5-6 minutes until the sauce thickens.

Step 3: Make the Mushroom Sauce

• 20 oz condensed mushroom soup
• 2 tbsp Worcestershire sauce
• 1 tbsp dijon mustard

Whisk the condensed mushroom soup, Worcestershire sauce, and dijon mustard into the thickened sauce until smooth and well combined.

The mixture should be creamy and uniform.

Step 4: Mix the Casserole Ingredients

• rotini noodles (from Step 1)
• 2 cups sliced mushrooms
• 2 carrots, sliced
• 2 cups cooked roast beef, cubed
• 2 tsp dried thyme
• 1 tsp kosher salt
• 1/2 tsp coarse ground black pepper
• sauce (from Step 3)

In a large mixing bowl, combine the drained rotini noodles (from Step 1), sliced mushrooms, sliced carrots, cubed cooked roast beef, dried thyme, kosher salt, coarse ground black pepper, and the sauce from Step 3.

Mix everything thoroughly so all ingredients are evenly coated in sauce.

I like to gently toss everything together to avoid breaking up the cubes of roast beef.

Step 5: Assemble and Bake the Casserole

• 1 1/2 cups shredded mozzarella cheese
• mixture (from Step 4)

Transfer the mixture from Step 4 into a large baking dish and spread it out evenly.

Sprinkle the shredded mozzarella cheese over the top.

Bake in the preheated oven for 20-25 minutes, or until the top is golden brown and bubbly.

For extra flavor, I sometimes add a pinch of fresh herbs before serving.