Sweet Potato Casserole with Streusel Topping and Marshmallows

This sweet potato casserole recipe has been a staple on our family’s table for nearly 15 years. After making this recipe dozens of times, our easy to follow directions, tips for success, and detailed step-by-step photos will ensure you can make a drool-worthy holiday side on your first try.

Everyone gets their favorite holiday recipes from somewhere. A family recipe that’s passed down from generation to generation. From a friend after a friends holiday gathering. A Pinterest pin you clicked on one time that turned out great. Or in my case, from an old magazine where I snapped a blurry cell photo picture of a recipe that was crammed into the bottom third of a page while waiting for my appointment at my dentist’s office.

This sweet potato casserole has been 15-years in the making, after lots of iterations based on that magazine recipe I snapped a picture of all those years ago. It’s become one of the recipes I get asked for the most from family and friends! So, it was time to officially document it and share it with all of you too.

If you love our sweet potato casserole recipe, then you’ve got to try our cheesy potato casserole and our lightened up mashed potatoes too!

Why You’ll Love Our Sweet Potato Casserole with Marshmallows

Always a crowd pleaser! Everyone LOVES this casserole. It’s such a big hit that at this point it’s just a fact that I will be brining this to Thanksgiving.

Streusel topping AND marshmallows. I mean, why decide on a streusel topping or marshmallows when you can have both?! It’s the double whammy your sweet potatoes have been needing.

Option to make ahead for easy holiday prep! We’ve detailed two ways you can make this side dish ahead of time (either a few days ahead or up to a few months ahead!) in the ‘Can you Make Sweet Potato Casserole Ahead of Time?’ section below.

Ingredients for Sweet Potato Casserole with Crumble Topping and Marshmallows

For the Sweet Potatoes

• Sweet potatoes. You’ll need 4-5 medium sweet potatoes for this recipe.
• Granulated sugar. Just enough to sweeten our sweet potato mixture a little bit before we add our toppings.
• Milk. We use 2% milk when making this recipe, but it has also turned out great with half-n-half, whole milk, or heavy cream if that’s what you have in your fridge.
• Large eggs. Eggs act as a binder to help hold our ingredients together, and also creates a light and moist filling.
• Salted butter. Butter adds richness and flavor to our casserole, and also helps with the structure of our sweet potato base.
• Vanilla extract. Adds richness and enhances the flavors in the dish.

For the Streusel Topping & Marshmallows

• All-purpose flour. Helps hold our ingredients together and creates a crumbly texture for our topping.
• Brown sugar. Used to sweeten our streusel topping.
• Old-fashioned oats (aka rolled oats). Adds lovely texture to our dish, making a robust streusel topping.
• Salted butter. Used to make our crumble topping.
• Mini Marshmallows. The final touch to our casserole, we toast these up right at the end for the perfect marshmallow topping.

Get the full recipe, with all the measurements and directions, at the bottom of this post in the recipe card.

How to Make Our Sweet Potato Casserole Recipe

Preheat your oven to 350°.

Place the cubed sweet potatoes in a large stockpot and add enough water to cover them by about 1″.

Bring to a boil and then reduce the heat, cooking the potatoes uncovered until tender (about 10-12 minutes).

While the potatoes are cooking, make the streusel topping by combining the flour, brown sugar, oats and salt in a medium mixing bowl. Add in the COLD butter.

Using a pastry cutter (or two forks, or your hands), cut in the butter until the streusel mixture is crumbly. Set aside.

When the sweet potatoes are fork tender, drain the potatoes. Either return them to the pan and mash with a potato masher or use a potato ricer to mash and return them to the pan (this is what is shown).

Once the sweet potatoes are mashed to your liking, add the sugar, milk, eggs, butter and vanilla extract to the potatoes. Stir (or continue to use your potato masher) to combine.

Transfer the potato mixture to an oven save 9×13 baking dish.

Spread the potato mixture into an even layer.

Sprinkle the streusel topping over the mashed sweet potato mixture and spread into an even layer.

Bake uncovered until topping the streusel topping is golden brown (about 40-45 minutes).

Top with mini marshmallows, spreading them into an even layer over the streusel topping.

Change oven to the low broil setting, and broil until the marshmallows are puffed up and golden (about 30-45 seconds; watch them closely!).

Recipe Variations

Add (or swap in) pecans to your crumble topping. If desired, add in up to ½ cup of chopped pecans to your oatmeal streusel topping, or swap use them in place of the oats if desired.

Add some warm fall spices. Adding ½ – 1 teaspoon of cinnamon or pumpkin pie spice to your streusel topping mixture is a great way to incorporate warm fall spices into this side dish.

Tips for Making the Best Sweet Potato Casserole

Use a potato ricer for ultra velvety and smooth sweet potatoes. This tool is what’s needed to make your mashed potatoes extra drool-worthy. While I love using a regular potato masher most of the year, I’ve found taking the extra time to use the ricer really takes this dish to the next level.

If you’re going to brown your marshmallows under the broiler, watch them closely! I’ve definitely made the mistake of getting distracted while my casserole is under the broiler and burning my marshmallows… don’t do it! This will take less than a minute, so make sure you’re watching the marshmallows closely. Once they start to puff up, it’ll be close to the time to pull your dish out of the oven.

Can you Make Sweet Potato Casserole Ahead of Time?

Yes! There are a few ways to make your sweet potato casserole with crumble topping and marshmallows ahead of time.

To prep your casserole 2-3 days ahead of time, prepare the filling and place it into the 9×13 pan. Do not bake it. Cover the pan with tinfoil and place it into the fridge. Prepare the topping as directed and store it separately from the casserole. When ready to bake, sprinkle the streusel topping over the mashed sweet potato base and bake as directed in the recipe card.

To prep your casserole up to 3 months ahead of time, prepare the filling and place it into the 9×13 pan. Do not bake it, allow it to cool fully, then cover the pan with two layers of tinfoil, and place it into the freezer. Thaw the casserole it in the fridge overnight before you bake it. If the filling has separated, simply mix it together with a spoon or hand mixer to re-combine. Add the streusel topping and bake as directed.

Storage and Reheating Instructions

Store leftovers in an airtight container in the fridge for up to 4 days. Reheat individual portions in the microwave until warmed to your preferred temperature.