Loaded Mashed Potato Casserole (Leftover Recipe)

Looking for a leftover mashed potato recipe? This Loaded Mashed Potato Casserole is the most delicious way to use up leftover mashed potatoes. It’s loaded with bacon, cheese and sour cream!

Thanksgiving is one of my favorite holidays, but with a gathering of just five people, we’re often stuck with quite a bit of leftovers after the big meal.

I’m prepared for the fact that even the smallest Cajun turkey will have us eating turkey sandwiches for several days. And leftover baked ham with pineapple sauce can always turn into ham and bean soup.

And for some reason, I find it impossible to make a small batch of mashed potatoes. Even when I limit it to one small potato per person, somehow once they’re all mashed up, I have enough to serve an army.

Then the question becomes, what to do with leftover mashed potatoes?

While you can simply reheat leftover mashed potatoes and drizzle them with homemade gravy a second time around, use them on top of mini shepherd’s pie, or even make potato cakes, my favorite way to serve leftover mashed potatoes a second time is this Loaded Mashed Potato Casserole.

How long are leftover mashed potatoes good for in the fridge?

As long as they are refrigerated promptly (no more than 2 hours after serving) and covered tightly, mashed potatoes from your holiday dinner will last about 3 or 4 days. This gives you plenty of time to gather the ingredients and make these loaded mashed potatoes.

What to do with leftover mashed potatoes:

The easiest way to reheat mashed potatoes is to simply spread them in a buttered casserole dish, cover them with foil, and bake at 350 degrees F until they are completely heated through. Thanksgiving rice is also great reheated this way.

But why not add some extra flavor before you reheat? That’s where this loaded mashed potato casserole recipe comes in.

What you’ll need for this loaded mashed potato casserole:

• mashed potatoes – use whatever type of mashed potatoes you have on hand for this leftover mashed potato recipe. I usually make Greek yogurt mashed potatoes for Thanksgiving, and use the leftovers here.
• sour cream – this adds some moisture back into the mashed potatoes, which tend to dry out when they’re heated up a second time.
• garlic powder – I normally use fresh garlic for just about everything, but I actually love the flavor of garlic powder in mashed potatoes!
• sharp cheddar cheese – because they’re not LOADED mashed potatoes unless we add cheese! You can use any type of cheese you want.
• bacon – make a quick batch of oven baked bacon and crumble it up. If turkey bacon is more your speed, check out my tutorials on how to cook turkey bacon in the oven and turkey bacon in an air fryer!
• red onion – I add quite a bit of onion to this loaded mashed potato casserole for added flavor. You can also use white or yellow onion.
• green onion – yes, a second type of onion! I like to add these for color.
• parsley – this is mainly for color, but you can skip it if you don’t have any on hand.
• cheese crackers – I love adding crushed cheese crackers (like Cheez-Its or Goldfish) to the top of this leftover mashed potato casserole for a bit of crunch. You can also use Ritz crackers or potato chips!
• butter – tossing the crackers in a bit of melted butter ensures they’ll get nice and golden brown on top of the casserole.

Tips for making this leftover mashed potato recipe successful:

This recipe works great with leftover mashed potatoes (or even leftover blue cheese mashed potatoes), but you can also make it starting with fresh mashed potatoes (i.e. make mashed potatoes specifically in order to make this recipe).

If using leftover mashed potatoes, the potatoes do need to be slightly warmed before stirring in the other ingredients.

Cold mashed potatoes are very hard to stir and incorporate with the other ingredients. Trust me, just warm them up a little and it will be so much easier.

These baked mashed potatoes are very adaptable to your family’s preferences and whatever ingredients you happen to have on hand.

Omit the bacon for a vegetarian loaded mashed potato casserole. Use chives instead of parsley. You can even use Parmesan cheese instead of cheddar in this leftover mashed potato recipe.

I love a scoop of this loaded mashed potatoes recipe alongside a helping of leftover Thanksgiving salad or Christmas salad.

Can I freeze this loaded mashed potatoes casserole?

If you make these loaded mashed potatoes using leftover mashed potatoes, I do NOT advise freezing it and reheating it again.

As a general rule of thumb for food safety, you only want to reheat leftovers once. Anything left over after that, you should discard.

However, if you make this recipe using “fresh” mashed potatoes (mashed potatoes you made immediately before making this casserole), you can freeze it.

Bake the frozen casserole straight from the freezer at 350 degrees F until the internal temperature of the casserole reaches at least 165 degrees F.

Psst – if you love the flavors in this loaded mashed potatoes recipe, you will also like my baked potato pizza!

Note: This loaded mashed potatoes recipe was originally published in 2013. The recipe was updated in 2022 to be even better, the photos were reshot, and the post was revised accordingly. The original photo appears below.