Creamy, crunchy, and endlessly comforting, this Green Bean Gratin is a weeknight hero and a holiday table favorite all in one. Imagine tender green beans bathed in a mushroomy, cheesy sauce and finished with a golden layer of French fried onions — simple, satisfying, and reliably delicious. Fun fact: gratins began in French country kitchens as a way to turn humble ingredients into something special, and this version follows that tradition perfectly.

This recipe is perfect for cooks who want big flavor with minimal fuss. It’s quick to assemble, uses pantry-friendly ingredients, and delivers a crowd-pleasing result that kids and adults love. If you’re already a fan of casserole classics, you’ll appreciate how this one leans into texture and depth — and if you like other green bean twists, check out our take on the best green bean casserole for more inspiration. Ready to get cozy with an easy, delicious gratin? Let’s cook!

What is Green Bean Gratin?

Who named this dish “gratin” anyway — does it wear a tiny beret while toasting its onions? In all seriousness, a gratin refers to a dish finished with a browned crust, and this Green Bean Gratin proudly sports a crispy, cheesy top over soft, seasoned green beans. Why the extra flair? Because a little crunch makes every bite sing.

Some say this kind of comfort food proves that “the way to a man’s heart is through his stomach.” Whether you’re courting someone special or simply feeding a hungry household, this dish has charm. Give it a try and see if it becomes your new go-to side (or sneakily satisfying main).

Why You’ll Love This

This gratin is irresistible for three big reasons. First, the main highlight: the creamy mushroom-and-cheese sauce clings to the beans, creating a rich, comforting mouthfeel that contrasts beautifully with the crispy fried onions on top. Second, making it at home is cost-effective — a single can of soup and a bag of beans go a long way compared to store-bought sides or restaurant orders. Third, the flavorful toppings — sharp cheddar and crunchy onions — elevate simple ingredients into something memorable.

Savoury, slightly nutty cheese, a whisper of garlic, and bubbly, golden edges make every forkful satisfying. If you enjoy a cheesy green bean spin, you might also like our lighter take in the cheesy garlic green beans, which emphasizes garlic and fresh herbs. Give this gratin a spot on your table and see how quickly it disappears.

How to Make

Quick Overview

This recipe is straightforward and forgiving, ideal for beginners and busy cooks. You’ll mix green beans with a creamy soup base, fold in cheese, top with more cheese and French fried onions, and bake until bubbly and golden. The star elements are the creamy sauce and the crispy finish. Prep time is about 10 minutes, and baking is 25 to 30 minutes, so plan for roughly 35 to 45 minutes total.

Ingredients

1 lb green beans, trimmed and rinsed
1 can (10.75 oz) cream of mushroom soup, room temperature if possible
1 cup French fried onions, divided (keep half for stirring and half for topping)
1 cup shredded cheddar cheese, divided (half stirred in and half for topping)
1/2 teaspoon garlic powder
Salt and black pepper to taste (about 1/2 teaspoon salt and 1/4 teaspoon black pepper as a starting point)
1/4 cup milk, room temperature

Directions

1. Preheat your oven to 375°F (190°C). Lightly grease a 9×9 baking dish or a similar-sized casserole dish so nothing sticks.
2. In a large mixing bowl, combine the trimmed green beans, cream of mushroom soup, milk, garlic powder, salt, and pepper. Stir until the sauce evenly coats the beans. Fold in half of the shredded cheddar cheese (about 1/2 cup) and half of the French fried onions (about 1/2 cup) so they’re distributed through the mixture.
3. Transfer the green bean mixture into the prepared baking dish and spread it into an even layer. Sprinkle the remaining shredded cheddar cheese evenly across the top, followed by the remaining French fried onions for a crunchy finish.
4. Bake in the preheated oven for 25 to 30 minutes, or until the casserole is bubbly and the top is golden brown. If the top browns too quickly, tent loosely with foil for the last 5–10 minutes. Let the gratin rest for 5 minutes before serving so it sets slightly.

What to Serve With

Pair this Green Bean Gratin with roasted or mashed potatoes for a comforting plate, or balance it with a light protein like roast chicken, pork loin, or grilled salmon. For a fresher contrast, serve alongside a crisp green salad with a lemon vinaigrette, or a simple tomato and cucumber salad. Holiday tables will appreciate it beside glazed ham and dinner rolls, while weeknight dinners pair well with baked chicken breasts and steamed rice. For drinks, a medium-bodied white wine or a sparkling water with lemon cleanses the palate nicely.

Top Tips for Perfecting

• Ingredient substitutions: Use cream of celery or cream of chicken soup if you prefer, and swap half the cheddar for Gruyère for a nuttier note. For a dairy-free version, try a mushroom-based plant milk and a dairy-free shredded cheese, though texture will differ.
• Timing adjustments: If your green beans are thick, blanch them in boiling water for 2 minutes and shock in ice water before mixing to ensure tenderness after baking.
• Flavor enhancements: Stir in a teaspoon of Dijon mustard or a tablespoon of finely chopped fresh herbs (thyme or parsley) to lift the flavor. A pinch of smoked paprika adds a gentle smokiness.
• Common mistakes to avoid: Don’t skip seasoning — the soup base benefits from salt and pepper. Avoid adding too much milk, which can make the gratin runny; 1/4 cup is enough.
• Make-ahead tip: Assemble the casserole up to the point of baking, cover, and refrigerate for up to 24 hours. Add an extra 5–10 minutes to bake time if chilled.

Storing and Reheating Tips

Refrigeration: Store leftovers in an airtight container for up to 3 days. The texture of the fried onions will soften over time, but the flavors remain.

Freezing: You can freeze the assembled gratin (before baking) for up to 2 months. Wrap the dish tightly with plastic wrap and foil. Thaw overnight in the refrigerator before baking; you may need an extra 10–15 minutes in the oven.

Reheating: Reheat individual portions in the microwave for 1–2 minutes until warmed through, though the topping won’t be as crisp. For best results, reheat in a 350°F (175°C) oven for 10–15 minutes to revive the top, or broil for 1–2 minutes while watching closely to crisp the onions.

FAQs

Can I use fresh mushrooms instead of cream of mushroom soup?
Yes. Sauté 1 cup of sliced mushrooms in a little butter until browned, then stir them into a simple béchamel (butter, flour, milk) to replace the canned soup. This adds more depth but increases prep time.

Is there a low-fat version of this gratin?
You can use low-fat milk and reduced-fat cheese, and swap the French fried onions for a toasted breadcrumb topping made with a little olive oil. The result will be lighter but slightly less rich.

Can I make this gluten-free?
Use a gluten-free cream of mushroom soup and gluten-free French fried onions or substitute with gluten-free panko breadcrumbs. Check labels to be sure all products are certified gluten-free.

How do I prevent the topping from getting soggy?
Add the fried onions right before baking and avoid covering the dish during the last 10 minutes of baking. For extra crunch, add half of the topping halfway through baking and the rest in the final minutes.

Can I add other vegetables to the gratin?
Absolutely. Blanched carrots, asparagus tips, or niblet corn can be mixed in. Make sure any added vegetables are pre-cooked or blanched so everything finishes cooking evenly.

Conclusion

This Green Bean Gratin is an easy, comforting dish that brings creamy texture and a crispy finish to your table with minimal fuss. It’s budget-friendly, family-approved, and flexible enough to adapt to what you have on hand. If you want a classic reference or an inspired variation, see Food52’s Green Bean Gratin recipe for another delicious take and ideas to customize your own. Give this recipe a try at your next meal — you might just find a new favorite side to share with family and friends.