When the turkey gravy starts bubbling around the pieces of turkey, the filling is already doing its job: bringing the leftovers together instead of letting them dry out in the oven. I like this casserole because it turns cooked turkey, gravy, and a bag of frozen peas and carrots into a hot, hearty center under a layer of mashed potatoes.
The potatoes need to be easy to spread before they go on top. A little milk loosens prepared mashed potatoes so they cover the filling without dragging it around, and sharp cheddar adds a savory finish as the casserole bakes. Once the top is golden and the edges are bubbling, you have a cozy turkey and mashed potato casserole with distinct layers in every scoop.
Kitchen Note
Stir the milk into the mashed potatoes before they go anywhere near the filling. Stop when they spread easily; potatoes that are too stiff can pull the turkey layer out of place as you cover it.
Save this Thanksgiving leftover turkey and mashed potato casserole for a warm, cheesy way to turn cooked turkey into a full-pan meal.
Why the Turkey Filling Goes Into the Oven Already Hot
This casserole has two layers that heat differently. The turkey filling is dense with cooked meat and gravy, while the mashed potatoes sit on top and take the direct heat first. Bringing the filling to a hot simmer on the stove gives the turkey and vegetables a head start, so the oven can finish the layers together instead of spending the whole bake trying to warm the center.
That’s also why the bubbling filling matters more than a browned top by itself. The foil keeps the casserole covered for the first part of baking; uncovering it lets the cheddar and potatoes finish without trapping all that steam. A casserole that looks ready around the edges still needs a hot center, so check the middle before you take it out. Then give it the full rest before serving so the layers settle instead of running together on the plate.
The Leftover Ingredients That Shape Every Layer
- Cooked turkey — Chopped turkey gives you neat, distinct bites; shredded turkey spreads through the gravy for a more even filling. Either works here, so use the texture you have on hand.
- Turkey gravy — Gravy binds the meat and vegetables into a moist filling and brings the turkey flavor through the whole dish. Homemade or prepared turkey gravy both fit; use one you like on its own, since it’s doing more than adding moisture.
- Frozen peas and carrots — The frozen mix saves prep and goes right into the skillet with the filling ingredients. Keep the pieces reasonably small so they sit comfortably under the potato topping.
- Prepared mashed potatoes and milk — The potatoes make a soft, substantial top layer, and the milk adjusts their consistency for spreading. Prepared potatoes vary in firmness, so judge by how easily they move across the filling rather than by appearance in the bowl.
- Sharp cheddar — Its stronger, savory taste stands up to the mild potatoes and gravy. Shredded sharp cheddar gives the top its cheesy finish; a milder cheddar will work, but the topping will taste less pronounced.
From Simmering Turkey to a Cheesy Potato Top
Soften the Onion and Celery
Heat the oven to 375°F and coat a 9×13-inch baking dish with nonstick cooking spray. Melt the butter in a 12-inch skillet over medium heat, then add the finely chopped onion and chopped celery. Cook for 4–5 minutes, stirring, until both vegetables have softened. If they’re still firm, give them another moment in the skillet before adding the rest.
Bring the Turkey Filling to a Simmer
Stir in the peas and carrots, cooked turkey, turkey gravy, and black pepper. Cook for 5–7 minutes, stirring often, until the mixture is hot and simmering. Stir around the bottom and edges of the skillet so the gravy heats evenly and nothing catches. You’re looking for small bubbles through the filling, not just a warm pan with a cool center.
Loosen the Mashed Potatoes
Stir the milk into the prepared mashed potatoes until they’re easy to spread. Work it through the potatoes rather than pouring it over one spot and leaving a thin patch. The finished mash should move across the filling without needing to be pressed down hard. If it’s still stiff, keep stirring until the texture is even.
Layer, Cover, and Finish the Bake
Spread the hot turkey mixture in the prepared baking dish, then spread the mashed potatoes evenly over it and sprinkle with cheddar. Cover the dish with foil and bake for 20 minutes. Remove the foil and bake for another 10–15 minutes, until the filling is bubbling and the center reaches 165°F. Let the casserole rest for 10 minutes before serving; cutting into it right away makes the layers harder to portion neatly.
Three Small Changes That Keep the Casserole Flexible
Choose chopped turkey for distinct bites
Use chopped rather than shredded cooked turkey when you want the pieces to stand out in the gravy. The filling will feel chunkier and each serving will have more defined bites; shredded turkey gives it a more uniform texture.
Leave off the cheddar for a milder top
Skip the shredded cheddar if you want the mashed potatoes to be the main flavor on top. You’ll lose the sharp, cheesy finish, but the turkey, gravy, and potato layers still make a complete casserole.
Make a gluten-free version
Choose gluten-free turkey gravy and prepared mashed potatoes, and check that the other packaged ingredients are gluten-free too. The filling and topping stay in the same layers; gravy brands can differ in thickness, so use one that gives the turkey mixture a cohesive, spoonable texture.
Storage and Reheating
- Refrigerator: Cover leftover casserole and refrigerate it for 3–4 days. The potato topping will firm up as it chills.
- Freezer: Freeze cooled portions in airtight, freezer-safe containers for best quality within 2–3 months. Thaw overnight in the refrigerator before reheating.
- Reheating: Warm a covered portion in a 350°F oven until hot throughout, or microwave an individual serving in short bursts. Leaving the casserole uncovered in the oven can dry the potato topping.
Questions That Come Up With Turkey and Potato Casserole
Thanksgiving Leftover Turkey and Mashed Potato Casserole
Ingredients
Equipment
Method
- Heat the oven to 375°F.
- Coat a 9x13-inch baking dish with nonstick cooking spray.
- Melt the butter in a 12-inch skillet over medium heat.
- Add the onion and celery and cook for 4–5 minutes, stirring, until softened.
- Stir in the peas and carrots, turkey, gravy, and black pepper; cook for 5–7 minutes, stirring often, until the mixture is hot and simmering.
- Stir the milk into the mashed potatoes until they are easy to spread.
- Spread the turkey mixture in the prepared baking dish.
- Spread the mashed potatoes evenly over the turkey mixture.
- Sprinkle with the cheddar.
- Cover the dish with foil and bake for 20 minutes.
- Remove the foil and bake for 10–15 minutes, until the filling is bubbling and the center reaches 165°F.
- Rest the casserole for 10 minutes before serving.