Sweet Potato Casserole with Marshmallows and Cinnamon Streusel — The Ultimate Thanksgiving Side Dish

There’s a warm, sweet nostalgia that comes with a bubbling pan of sweet potato casserole fresh from the oven. As a kid I remember sneaking into the kitchen while my grandmother arranged the marshmallows just so — the way they toasted to a caramelized gold always felt like a tiny holiday miracle. Over the years I’ve tweaked her recipe to add a buttery cinnamon streusel for extra texture, and it’s become the dish everyone requests at family gatherings. Sweet potato casserole has roots in American holiday traditions — especially Thanksgiving — where sweet, comforting sides symbolize abundance and togetherness. This version, topped with gooey marshmallows and a crisp cinnamon streusel, bridges old-school comfort with crunchy, modern appeal.

Who is this recipe for?

• This sweet potato casserole is perfect for holiday hosts, busy parents, weeknight planners who want an easy but impressive side, and beginners looking for a forgiving, crowd-pleasing recipe.

Core ingredients overview:

• This recipe centers on 4 cups cooked and mashed sweet potatoes blended with brown sugar, milk, melted butter, vanilla, and salt for a creamy base. A crunchy streusel of flour, oats, brown sugar, cinnamon, and softened butter gives texture, and 2 cups mini marshmallows top the dish for sweet, toasty finish. This dish combines sweet potatoes, brown sugar, butter, and warm spices to create a creamy, textured, and nostalgic side everyone will love.

Tools & Ingredients

Tools you will need:

• 9×13-inch baking dish (greased)
• Large mixing bowl
• Mixing spoon or rubber spatula
• Measuring cups and spoons
• Potato masher or ricer (or stand mixer)
• Medium bowl for streusel
• Pastry cutter or fork (to cut in butter)
• Oven (preheated to 350°F / 175°C)

Ingredients (with a short benefit for each):

• 4 cups sweet potatoes, cooked and mashed — adds natural sweetness, fiber, and vitamin A
• 1/2 cup brown sugar — deep, molasses-like sweetness that complements sweet potatoes
• 1/2 cup milk — creates a smooth, creamy texture in the filling
• 1/4 cup butter, melted — enriches the custard-like base with buttery flavor
• 1 teaspoon vanilla extract — enhances overall flavor and adds warmth
• 1/2 teaspoon salt — balances sweetness and brightens flavors
• 2 cups mini marshmallows — provides the signature gooey, toasted topping guests love
• 1/2 cup all-purpose flour — forms the base of the streusel for structure
• 1/2 cup rolled oats — adds chew and wholesome texture to the streusel
• 1/2 cup packed brown sugar — sweetens and caramelizes the streusel topping
• 1 teaspoon ground cinnamon — adds warm spice and aroma to the streusel
• 1/4 cup butter, softened — binds the streusel and creates crisp, buttery crumbs

Instructions

1. Preheat the oven to 350°F (175°C).
2. In a large bowl, mix the mashed sweet potatoes, 1/2 cup brown sugar, milk, melted butter, vanilla extract, and salt until smooth.
3. Pour the sweet potato mixture into a greased 9×13-inch baking dish and spread it into an even layer.
4. In another bowl, combine the flour, oats, 1/2 cup brown sugar, and cinnamon. Cut in the softened butter with a pastry cutter or fork until the mixture is crumbly.
5. Sprinkle this streusel mixture evenly over the sweet potato layer.
6. Bake in the preheated oven for 25 minutes.
7. Remove from the oven and top with mini marshmallows, spreading them evenly across the casserole.
8. Return to the oven and bake for an additional 10 minutes or until the marshmallows are golden brown and the streusel is crisp.
9. Let cool slightly before serving so the casserole sets and is easier to portion.

FAQ

Q: Can I freeze this recipe?
A: Yes — you can assemble the casserole up to step 6 (before adding marshmallows), cover tightly with foil, and freeze for up to 2 months. When ready, bake from frozen at 350°F (175°C) for about 35–45 minutes, then add marshmallows and bake another 10 minutes until golden.

Q: What can I use instead of marshmallows?
A: If you prefer not to use marshmallows, try a brown sugar and pecan topping or a layer of mini meringues. For a less sweet option, skip the marshmallows and double the streusel for extra crunch.

Q: Can I make this recipe dairy-free or vegan?
A: Yes — substitute plant-based milk and use vegan butter or coconut oil for the melted and softened butter. Use vegan marshmallows (check labels) to keep it fully vegan.

Q: Can I prepare the sweet potatoes ahead of time?
A: Absolutely. You can cook and mash the sweet potatoes 1–2 days ahead and store them in the fridge. Assemble and bake when ready for best texture.

Tips & Tricks

• Dry your mashed sweet potatoes well: If they’re too watery, the filling will be loose. After boiling or roasting, drain and return to the pot over low heat for a minute to evaporate excess moisture.
• Toast the oats lightly before making the streusel for extra nutty flavor and a crisper topping.
• Watch the marshmallows closely in the final minutes — they can go from golden to burnt quickly. If they’re browning too fast, tent the dish loosely with foil.
• For even heating, mash the sweet potatoes until smooth and avoid large lumps so the filling sets uniformly.

Conclusion

For more variations and step-by-step photos, you might enjoy this Sweet Potato Casserole with Marshmallows and Streusel guide: Sweet Potato Casserole with Marshmallows and Streusel. If you want a classic take with a slightly different streusel, check this helpful resource: Sweet Potato Casserole –. For another trusted recipe and tips on texture and timing, see Sweet Potato Casserole Recipe | My Baking Addiction.

Enjoy this cozy, crowd-pleasing dish — and don’t forget to share it with friends and family!