To make green bean casserole, stir cooked green beans into a creamy mushroom sauce, spread the mixture in a shallow baking dish, and top it with crispy fried onions. Bake until the sauce is bubbling and the topping is browned. The dish is a classic Thanksgiving side because it can be assembled ahead and finished while the turkey rests. For Thanksgiving 2026, see the Thanksgiving guide and the Thanksgiving sides shopping plan.
Build the sauce and beans
The familiar version uses condensed cream of mushroom soup thinned with a little milk, plus cooked green beans and a share of the onions stirred into the sauce. You can also make a from-scratch sauce by cooking mushrooms in butter, stirring in flour, then whisking in milk or stock until it is thick enough to coat the beans. Season with salt, pepper and a splash of soy sauce if you like more savory depth. Taste before adding much salt; canned soup and fried onions are already salty.
Use about 1½ to 2 pounds of green beans for a 2-quart dish that serves around eight, or scale to your guest list. Blanch fresh beans in boiling water until they are bright and just tender, then cool them so they do not keep cooking. If you use frozen beans, thaw and drain them well. Canned beans should be drained and rinsed.
Top and bake
Spread the mixture in a lightly greased 2-quart or 9-by-13-inch dish. Bake in a moderate oven, often around 350°F, until the sauce bubbles at the edges, usually 25 to 35 minutes if the dish started at room temperature, longer if it is fridge-cold. Add the remaining crispy onions for the last few minutes so they brown without burning. If you need the oven at 325°F for the turkey, the casserole can cook at that temperature; give it more time and wait for visible bubbling.
Serve and store safely
Keep the finished casserole hot, above 140°F, if it will sit on the table, and refrigerate leftovers within 2 hours. Use them within 3 to 4 days, as in the USDA turkey roasting guide leftover guidance also summarized in how long Thanksgiving leftovers last. Related: how to make gravy.
Frequently asked questions
Can I assemble green bean casserole ahead?
Yes. Mix the beans and sauce, cover, and refrigerate up to a day. Add the crispy onion topping just before baking so it stays crunchy.
Fresh, frozen or canned beans?
Any of the three work. Blanch fresh beans until just tender, drain frozen beans well, and drain canned beans so the sauce does not turn watery.
How long do leftovers last?
Refrigerate the casserole within 2 hours and use it within 3 to 4 days. Reheat leftovers until steaming hot throughout.
Helpful kitchen tools
- OXO Good Grips 2-Cup and 4-Cup Glass Measuring Cup Set — Handy for milk, soup and sauce measurements.
- OXO Good Grips 11-Pound Digital Kitchen Food Scale — Weigh green beans so you can scale the casserole to your guest count.
- OXO Good Grips Chef’s Precision Digital Instant Read Thermometer — Useful the same day for the turkey, and to check that leftover casserole is steaming hot.
- Cuisinart Stainless 16-Inch Roasting Pan with Rack and Deluxe Basting Set — A roasting-pan rack is for the turkey; bake the casserole in its own shallow dish so both can share an oven more easily.
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