Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe

If you have a soft spot for comforting, cozy dishes packed with sweet, spiced flavors and irresistible textures, this Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe will quickly become your new favorite. It’s that perfect balance between creamy mashed sweet potatoes, fluffy toasted marshmallows, and a crunchy oat streusel topping that brings the perfect contrast in every bite. This casserole offers a nostalgic, warm taste that is so simple to make but feels extra special—just the kind of dish you want to share with family and friends around the table.

Ingredients You’ll Need

This recipe keeps things wonderfully straightforward, using essential pantry staples combined with fresh sweet potatoes to create layers of rich flavor and delightful texture. Each ingredient plays a key role in delivering that iconic sweet potato casserole experience—from the buttery mash to the crunchy streusel topping and gooey marshmallows.

• Butter (4 tablespoons cold + 2 tablespoons for mash): Adds richness and helps create that tender crumbly oat streusel and creamy mashed potatoes.
• Brown sugar (1/4 cup): Brings natural sweetness and caramel notes to the streusel, balancing the spices.
• Flour (1/4 cup): Helps bind the streusel topping and gives it that perfect crumble texture.
• Rolled/old fashioned oats (1/4 cup): Adds chewiness and heartiness to the topping for a satisfying crunch.
• Baking powder (1/2 teaspoon): Provides a touch of lift in the streusel topping for lightness.
• Pumpkin pie spice (1 teaspoon + 1/2 teaspoon): Infuses the potatoes and streusel with warm, autumnal spice that’s comforting and fragrant.
• Salt (pinch + 1 teaspoon): Balances the sweetness and enhances all the flavors beautifully.
• Sweet potatoes (3 medium): The star ingredient delivering natural sweetness, creamy texture, and gorgeous color.
• Milk (1/4 cup): Keeps the mashed potatoes smooth and creamy without overpowering.
• Mini marshmallows (3 cups): The crowd-pleaser layer that melts into delightfully gooey, toasted pockets on top.

How to Make Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe

Step 1: Prepare and Cook the Sweet Potatoes

Start by peeling and slicing your sweet potatoes into 1-inch rounds. Place these in a large pot with the teaspoon of salt and cover with cold water. This gentle start ensures they cook evenly and absorb just the right seasoning as they boil.

Step 2: Boil Until Tender

Bring the pot to a boil over high heat, then cover and cook the potatoes for 20 to 25 minutes. They are ready when you can easily pierce them with a fork—a sign that they’ll mash smoothly and blend perfectly with your spices and butter.

Step 3: Drain and Steam Off Excess Moisture

Carefully pour off the water and return the pot to the stove on medium heat. Leaving it uncovered, heat for a minute or two to evaporate any extra moisture. This step helps avoid watery mashed potatoes and gives a stable base for the rest of the dish.

Step 4: Mash the Potatoes with Flavor

Remove the pot from heat, then add the butter, milk, and pumpkin pie spice. Gently mash the potatoes until smooth but still fluffy. The spice adds a warm depth that complements the natural sweetness perfectly. Set this aside or transfer to an airtight container if prepping in advance.

Step 5: Make the Oat Streusel Topping

Cut your cold butter into small marble-sized pieces and combine with brown sugar, flour, oats, baking powder, pumpkin pie spice, and a pinch of salt in a mixing bowl. Using two forks, a pastry cutter, or your fingers, work the butter into the dry ingredients until crumbs about the size of large peas form. This streusel gives you that beautiful crunch and nutty texture on top.

Step 6: Prepare for Baking

Preheat your oven to 350ºF and grease a 2 ½ quart baking dish (similar sizes work too). Spread the mashed sweet potatoes evenly over the bottom of the dish, smoothing the surface for an even bake.

Step 7: Layer Marshmallows and Streusel

Scatter the mini marshmallows generously over the mashed sweet potatoes. Then sprinkle the oat streusel topping evenly on top. This layering creates a marvelous texture contrast with soft, sweet marshmallows and a crisp, crumbly oat crust.

Step 8: Bake to Perfect Golden Brown

Bake the casserole for 18-20 minutes in your preheated oven. Keep an eye on the top, so your marshmallows toast nicely without burning. When the topping is golden and bubbly, you know you’re close!

Step 9: Let It Rest

Remove the casserole from the oven and allow it to rest for at least 10 minutes before serving. This rest time lets the layers firm up slightly, making serving easier and more enjoyable by keeping those buttery, marshmallow layers perfectly intact.

How to Serve Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe

Garnishes

A sprinkle of chopped pecans or a light dusting of cinnamon on top after baking adds a beautiful finish and extra crunch. Fresh herbs like rosemary are unusual but can bring a surprising aromatic kick for adventurous palates.

Side Dishes

This casserole pairs wonderfully with savory mains like roasted turkey, glazed ham, or even a juicy pork loin. For a balanced meal, consider adding crisp green beans or a fresh spinach salad with tangy vinaigrette to cut through the richness.

Creative Ways to Present

For a festive touch, serve individual portions in small ramekins topped with a single toasted marshmallow and a drizzle of maple syrup. Or, try layering the casserole in a clear glass baking dish so guests can admire the beautiful layers before digging in!

Make Ahead and Storage

Storing Leftovers

Place leftover casserole in an airtight container and refrigerate for up to 3 days. The flavors actually deepen overnight, making your second helping even more delicious. Reheat gently to preserve the textures.

Freezing

To freeze, assemble the casserole but hold off on baking. Wrap tightly in plastic wrap and foil and freeze for up to one month. When ready to enjoy, thaw overnight in the fridge before baking as instructed.

Reheating

Warm leftovers in the oven at 325ºF for 15-20 minutes until heated through and the topping regains some crispness. Avoid microwaving if you want to keep the streusel crunchy and the marshmallows perfectly soft and melty.

FAQs

Can I use canned sweet potatoes for this casserole?

While fresh sweet potatoes offer the best texture and flavor, canned sweet potatoes can work in a pinch. Just be sure to mash them well and reduce added moisture for a firmer casserole.

Is there a substitute for marshmallows in the recipe?

If marshmallows aren’t your thing, try a crunchy pecan topping alone or swap marshmallows for a light dusting of brown sugar and cinnamon before baking to keep the sweetness but with a different texture.

Can I make the oat streusel gluten-free?

Absolutely! Use gluten-free oats and substitute the all-purpose flour with a gluten-free blend or almond flour to keep the cranberry topping crumbly without gluten.

What’s the best way to prevent the marshmallows from burning?

Keep a close eye during the last few minutes of baking and remove the casserole as soon as the marshmallows turn golden. If they brown too quickly, tent the dish loosely with foil.

Can I prepare the casserole the night before?

Definitely! You can prepare all three components separately and assemble them just before baking. This makes it perfect for busy holiday mornings or dinner prep ahead of time.

Final Thoughts

There is something truly special about a Sweet Potato Casserole with Marshmallows and Oat Streusel Recipe that brings warmth and joy to any meal. Whether it’s a holiday tradition or a simple family feast, this dish never fails to impress with its luscious layers of flavor and texture. I hope you have as much fun making and sharing it as I always do. Give it a try and watch it become a beloved classic in your kitchen!

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