These Cheesy French Onion Potatoes layer thin slices of Yukon Gold potato in a rich, creamy French onion sauce, then pile on Gruyère, Swiss, and mozzarella for a cheese pull in every bite.
Crispy fried onions on top add crunch, and the whole thing bakes low and slow until the potatoes turn tender and the sauce thickens around them. It's a great holiday side dish that's easy enough for any night of the week!
I make either this French onion potato casserole or my Creamy Scalloped Potatoes every Thanksgiving, but this is the one that gets the most people asking for the recipe.
One of my favorite things about this French onion soup potato bake is that I can put it together the day before. I layer everything into the dish, cover it, and stick it in the fridge. Then I can just pop it in the oven when it's time to eat! On a holiday when there's already a dozen other things going on, that's one less thing to think about.
Ingredients for French Onion Potato Casserole
This dish gets its deep, savory flavor from a can of condensed French onion soup, the same shortcut I use in my Slow Cooker French Onion Beef and Potatoes and my French Onion Beef Noodle Skillet.
For the potatoes, Yukon Golds hold their shape well as they bake, and red potatoes are the better swap if you need one, since starchier potatoes like russets tend to break down and turn mushy over a long bake. Slice them thin and even, about ⅛ inch, so every layer bakes through at the same pace.
Gruyère and Swiss are usually stocked in the specialty cheese case rather than in the pre-shredded bags, so look there if your grocery store carries them.
The crispy fried onions on top are optional, though I love them because they add a little crunch that you won't get otherwise!
See recipe card for quantities.
How to Make Cheesy French Onion Potato Casserole
Create the creamy French onion sauce
In a large bowl, whisk the condensed French onion soup, onion soup mix, heavy cream, sour cream, Worcestershire sauce, garlic powder, and black pepper until smooth. Add the Gruyère, Swiss, 1½ cups of the mozzarella, and the Parmesan to the sauce and stir until combined, saving the remaining mozzarella for the topping.
Layer the potatoes
Arrange one-third of the sliced potatoes in the baking dish.
Continue layering
Spoon one-third of the cheese sauce evenly over the top. Repeat the layers two more times, ending with a layer of sauce.
Bake, then top with cheese and return to oven
Cover the dish tightly with foil and bake for 70 minutes. Remove the foil and check that the potatoes are nearly fork-tender, then sprinkle the reserved mozzarella evenly over the top. Return the casserole to the oven, uncovered, for 15 to 20 minutes, until the potatoes are tender and the cheese is bubbling.
Top with fried onions and rest
Scatter the crispy fried onions and parsley over the top, then let the casserole rest for 15 minutes before slicing and serving.
Top Tips
- Slice the potatoes as evenly as possible, ideally with a mandoline, so every layer cooks at the same rate.
- Shred the cheese yourself instead of using bagged pre-shredded cheese. Bagged cheese is coated with starch to keep the shreds from clumping, and that coating can make the sauce grainy instead of smooth.
- If your slices come out thicker than ⅛ inch, add another 10 to 15 minutes to the covered bake time, then check again.
- Test doneness with a knife in the center of the dish, since the middle layers take the longest to soften.
- Add the fried onions after baking rather than before, since the oven's heat will burn them if they're in too long.
Variations
One of my favorite ways to change up this dish is to add layers of leftover shredded chicken or diced ham right under the sauce to make it a full meal.
I also love to add sautéed mushrooms to the sauce to give it more of an earthy, steakhouse feel.
Equipment
I bake this in a standard 9x13-inch ceramic baking dish, which heats up quickly and helps the potatoes cook through evenly during the covered bake.
A mandoline makes quick work of slicing all the potatoes to a consistent ⅛-inch thickness. This matters more in this recipe than in others because evenly sliced potatoes cook at the same rate.
Storage
This casserole is a great one to make ahead for a holiday. Assemble it up to 24 hours in advance, cover it, and keep it in the fridge unbaked, then bake it as directed once you're ready to serve. Remember to add a bit of time if you're cooking it straight from the fridge.
For longer storage, you can freeze it before baking for up to 2 months. Just thaw it overnight in the refrigerator first.
Once baked, refrigerate leftovers, covered, for up to 4 days, then reheat covered in a 325°F oven until warmed through, or microwave individual portions.
FAQs
It's not necessary, but you can if you prefer.
This recipe is built around thin potato slices for a scalloped-style texture, so I haven't tested it with frozen hash browns.
Potato thickness varies a lot depending on how you slice them, so if yours run thicker than ⅛ inch, they may need another 10 to 15 minutes covered before they're tender.
I don't recommend it. Russets are starchy and tend to break down and turn mushy over the long bake. Yukon Golds or red potatoes hold their slices much better.
Cheesy French Onion Potatoes
Ingredients
- 10.5 oz condensed French onion soup
- 1 packet dry onion soup mix
- 1½ cups heavy cream
- 1 cup sour cream
- 1 teaspoon Worcestershire sauce
- 1 teaspoon garlic powder
- ½ teaspoon black pepper
- 3 pounds Yukon Gold potatoes peeled and sliced ⅛-inch thick
- 1 cup Gruyère cheese shredded
- 1 cup Swiss cheese shredded
- 2 cups mozzarella cheese shredded, divided
- ½ cup Parmesan cheese grated
- 1½ cups crispy fried onions optional
- 2 tablespoons chopped parsley optional
Instructions
- Preheat the oven to 350°F and grease a 9x13-inch baking dish.
- Whisk together the French onion soup, onion soup mix, heavy cream, sour cream, Worcestershire sauce, garlic powder, and black pepper until smooth.
- Stir in the Gruyère, Swiss, 1½ cups of the mozzarella, and the Parmesan.
- Layer one-third of the potatoes in the dish, then spoon one-third of the sauce over the top. Repeat twice more, ending with a layer of sauce.
- Cover tightly with foil and bake for 70 minutes.
- Uncover, check that the potatoes are nearly fork tender, and sprinkle the remaining mozzarella over the top.
- Bake uncovered for 15-20 minutes, until the potatoes are tender and the cheese is bubbling.
- Top with crispy fried onions and parsley, then let rest 15 minutes before serving.
Notes
Nutrition
Nutrition Disclaimer
All nutritional information provided is an estimate. For specific dietary needs or concerns, we recommend consulting a nutrition calculator or a qualified expert.
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Karen Kelly
Karen Kelly is a nationally syndicated food and travel writer, founder of Seasonal Cravings, and co-founder of The Roam Report. She develops approachable seasonal recipes and covers travel and lifestyle trends. Her work has appeared in numerous media outlets, including Yahoo, Taste of Home, Apple News, NBC, FOX, and other national and regional publications.
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