Savory Pot Roast Casserole from Leftover Roast

Leftover pot roast casserole is a delicious beef-and-potato bake that gives your roast a tasty second life. This comforting casserole is quick to assemble and perfect for feeding a hungry family.

Pot roast is a classic for a reason — tender, flavorful, and satisfying. But leftovers can feel repetitive, and not everyone in my house gets excited about eating the same meal twice.

I don’t like wasting food, especially when beef is expensive, so I reinvent the leftovers into something new. This pot roast and au gratin potato casserole transforms leftover roast into a completely different, family-friendly dinner everyone enjoys.

It’s straightforward to make and comes together quickly, so it’s ideal for busy weeknights or when you want a comforting meal without a lot of fuss.

Ingredients

What you’ll need:

• Butter – Unsalted works best because pot roast and gravy can be salty.
• Vegetables – Diced white onion, peeled and sliced carrots, sliced celery.
• Leftover pot roast – Shredded into bite-sized pieces.
• Brown gravy – A few tablespoons of canned or prepared gravy.
• Boiling water – For the potato mix.
• Milk – Use whole milk for richness.
• Au gratin potatoes – Two 4.7 oz boxes (or the equivalent potato-and-sauce mix).

How to make

This recipe is an easy way to remake leftovers into a hearty casserole.

1. Preheat oven and prepare dish: Spray a 9×13″ baking dish with nonstick spray and set aside.

2. Sauté the vegetables: Melt 1 tablespoon of butter in a large skillet over medium heat. Add the diced onion, sliced carrots, and celery and cook 6–8 minutes until softened, stirring often.

3. Add the beef: Stir the shredded pot roast and about 1/3 cup brown gravy into the skillet. Cook just until the mixture is heated through, then remove from heat.

4. Make the potatoes: In a separate pot, melt the remaining butter with 4 cups of boiling water, stirring until the butter melts. Whisk in 1 cup milk and the two au gratin potato mix pouches until smooth and evenly combined. Let the mixture sit for a minute off the heat.

5. Assemble the casserole: Pour the potato mixture into the prepared baking dish. Spoon the pot roast and vegetable mixture over the potatoes and gently stir a few times to incorporate without overmixing.

6. Bake: Place the casserole in a 450°F oven and bake 35–40 minutes, or until the potatoes are tender and the top is set.

7. Rest and serve: Remove from the oven and let the casserole rest for about 5 minutes to thicken. Serve warm and enjoy.

Storing leftovers

Store any leftover casserole in an airtight container in the refrigerator for up to four days. Reheat in a low oven (or covered in the oven) until warmed through to preserve texture and flavor.

Tips and tricks

• Use unsalted butter so the casserole doesn’t become overly salty — pot roast and gravy often have enough seasoning already.
• If the casserole looks a bit loose when it comes out of the oven, don’t worry: it will thicken as it rests for the recommended five minutes.
• This is a great recipe for using up extra vegetables. Add leftover roasted Brussels sprouts, steamed broccoli, or a handful of frozen peas for more color and nutrition.
• No leftover pot roast? Substitute store-bought shredded beef or a small cooked roast that you shred with two forks.

Other ways to use leftover pot roast

If you enjoy this casserole, try other ideas for repurposing leftover pot roast: make grilled cheese sandwiches with roast beef and a melty cheese, turn it into a hearty soup, or use the beef as the filling for a shepherd’s pie-style dish. Leftovers are versatile and can be adapted to many comforting meals.