Slow Cooker Green Bean Casserole

Meggan Hill

5 from 40 votes

This post contains affiliate links, which means I may earn a commission if you purchase through those links (at no extra cost to you).

Pin ThisJump to Recipe

This Slow Cooker Green Bean Casserole is a great mix of convenience and from-scratch cooking and won’t take up any oven space. Start with frozen beans but make your own creamy mushroom sauce, then top the whole thing with plenty of crunchy fried onions.

A plate of green bean casserole.


 

I didn’t grow up eating Green Bean Casserole at Thanksgiving, but based on the recipe I see in Campbell’s magazine ads, I’m not sorry about it. Canned green beans with canned mushroom soup? I’m not a food snob, but that just doesn’t sound like my kind of thing.

So when I made Green Bean Casserole the first time, I kicked the cans. I’ve made Green Bean Casserole in the oven with fresh beans too, but my go-to is this version, in a slow cooker, with frozen green beans.

The Cream of Mushroom sauce takes about 10 minutes or so, and it’s worth every second. The flavor here is so much better than canned: Rich, savory mushrooms, heavy cream, and fresh garlic.

Toss the green beans in the sauce, then transfer the whole thing to your slow cooker. Just before serving, top the Green Bean Casserole with crispy French fried onions. Yes, those classic crunchy ones from a can. If it ain’t broken, don’t fix it.

Table of Contents

  1. Recipe ingredients
  2. Ingredient notes
  3. Step-by-step instructions
  4. Recipe tips and variations
  5. Slow Cooker Green Bean Casserole Recipe

Recipe ingredients

Labeled ingredients for slow cooker green bean casserole.

At a Glance: Here is a quick snapshot of what ingredients are in this recipe.
Please see the recipe card below for specific quantities.

Ingredient notes

  • Mushrooms: Use fresh mushrooms to make a quick from-scratch cream of mushroom sauce.
  • Frozen green beans: To substitute fresh beans, trim and chop 2 pounds of green beans. Blanch the beans in 4 quarts of boiling salted water for about 5 minutes, then drain well and plunge immediately in to an ice bath to stop the cooking.
  • Fried onions: To substitute bread crumbs for the canned fried onions, pulse 4 slices hearty white bread (torn into pieces) in a food processor or blender. You will have about 3 cups of crumbs. Stir in 3 tablespoons melted butter or olive oil and fry in a large skillet over medium-high heat until browned. Sprinkle over the casserole just before serving.

Step-by-step instructions

  1. In a large skillet or Dutch oven, melt butter over medium-high heat until foaming subsides. Add mushrooms, garlic, ¾ teaspoon salt, and ⅛ teaspoon pepper. Cook until the mushrooms have released most of their liquid, about 5 to 7 minutes.
Mushrooms cooking down in a stock pot.
  1. Stir in flour and cook for one minute. Whisk in broth, scraping up any brown bits from the bottom of the pan. Bring to a boil, whisking constantly.
Adding chicken broth to cooked mushrooms.
  1. Reduce heat to medium. Whisk in cream and simmer until the sauce has thickened, about 5 minutes. Season to taste with salt and pepper.
Adding cream to mushroom soup.
  1. Meanwhile, cook the beans in the microwave according to the package instructions (or microwave on HIGH power for 4 to 5 minutes; let stand 1 minute before removing from the microwave). Drain well (I like to use a salad spinner to spin them dry). Add the green beans to the pot with the mushroom sauce and toss until evenly coated. Transfer the beans and sauce to a crock pot.
A slow cooker full of green bean casserole.
  1. Cook on HIGH for 2 hours or LOW for 4 hours or until a thermometer inserted in to the middle of the casserole reaches 165 degrees. Top with canned fried onions immediately before serving.
A platter of green bean casserole.

Recipe tips and variations

  • Yield: This recipe makes about 10 cups of casserole, enough for 10 1-cup sized, side dish (you’ll be able to feed more than 10 people depending on how many sides you have at Thanksgiving).
  • Storage: Store leftovers covered in the refrigerator for up to 4 days.
  • Make ahead: You can make the mushroom sauce up to 2 days before. Cool and refrigerate. Since the sauce will be going in cold, increase the crockpot time to 3 hours on HIGH or 5 hours on LOW.
  • Blanch fresh green beans ahead: If using fresh beans instead of frozen, they may be blanched the night before, cooled, and stirred in the cooled mushroom sauce, and refrigerated overnight. Increase the crockpot time to 3 to 4 hours on HIGH or 5 to 6 hours on LOW .
  • Oven instructions: Follow the recipe as written through Step 5, but then instead of transferring the green bean mixture to a slow cooker, spread it in the bottom of a 3-quart or a 9×13 baking dish. Sprinkle with fried onions and bake at 425 degrees until the top is golden brown and the sauce is bubbling around the edges, about 15 minutes.
  • Small batch: Green bean casserole for two is made in the oven with 8 ounces frozen green beans.
  • Vegan Green Bean Casserole: Plant-based Green Bean Casserole made with cashew cream in a slow cooker.
  • Small army: To triple the recipe for 30 to 40 people, increase the ingredients as follows: ½ cup (1 stick) butter, 3 pounds white button mushrooms, 1 bulb garlic (9 to 10 cloves) 3 teaspoons salt, and ½ teaspoon pepper, 1 cup flour, 4 ½ cups chicken broth, 4 ½ cups heavy cream, 6 (12-ounce) packages of frozen cut green beans, and 3 cups canned fried onions (or more if desired).
  • Best Thanksgiving Slow Cooker Recipes: Discover the best slow cooker recipes for your Thanksgiving feast including turkey and all the classic sides. Free up oven and stove top space when you need it most by cooking one (or more!) Thanksgiving recipes in a crockpot.
A plate of roasted trukey, stuffing, vegetables, mashed potatoes and gravy, and cranberries.
A Classic Midwestern Thanksgiving: Perfect Roast Turkey, Mashed Potatoes with Gravy, Classic Bread Stuffing, Vegetable Casserole, Roasted Asparagus, and Cranberry Sauce with Apples.

Perfect Roast Turkey

The most Perfect Roast Turkey recipe relies on dry-brining and butter-basting for the juiciest, most delicious turkey you’ve ever had. Save your pan drippings too for an easy classic gravy recipe.

1 day 5 hours 30 minutes
View Recipe

More Thanksgiving recipes

Join Us

HUNGRY FOR MORE? Sign up for our weekly newsletter and follow along on Facebook, Pinterest, and Instagram for our latest recipes! Tag all your glorious creations #culinaryhill so we can eat vicariously through you.
Slow cooker green bean casserole on a patterned platter.

Slow Cooker Green Bean Casserole

By Meggan Hill
This Slow Cooker Green Bean Casserole is a great mix of convenience and from-scratch cooking and won't take up any oven space.
Prep Time 5 minutes
Cook Time 2 hours 20 minutes
Total Time 2 hours 25 minutes
Servings 10 servings (1 cup each)
Course Side Dish
Cuisine American
Calories 280
5 from 40 votes
ReviewPrint

Ingredients 

Instructions 

  • In a large skillet or Dutch oven, melt butter over medium-high heat until foaming subsides. Add mushrooms, garlic, ¾ teaspoon salt, and â…› teaspoon pepper. Cook until the mushrooms have released most of their liquid, about 5 to 7 minutes.
  • Stir in flour and cook for one minute. Whisk in broth, scraping up any brown bits from the bottom of the pan. Bring to a boil, whisking constantly.
  • Reduce heat to medium. Whisk in cream and simmer until the sauce has thickened, about 5 minutes. Season to taste with salt and pepper.
  • Meanwhile, cook the beans in the microwave according to the package instructions (or microwave on HIGH power for 4 to 5 minutes; let stand 1 minute before removing from the microwave). Drain well (I like to use a salad spinner to spin them dry).
  • Add the green beans to the pot with the mushroom sauce and toss until evenly coated. Transfer the beans and sauce to a crock pot.
  • Cook on HIGH for 2 hours or LOW for 4 hours or until a thermometer inserted in to the middle of the casserole reaches 165 degrees. Top with canned fried onions immediately before serving.

Recipe Video

Notes

  1. Mushrooms: Use fresh mushrooms to make a quick from-scratch cream of mushroom sauce.
  2. Frozen green beans: To substitute fresh beans, trim and chop 2 pounds of green beans. Blanch the beans in 4 quarts of boiling salted water for about 5 minutes, then drain well and plunge immediately in to an ice bath to stop the cooking.
  3. Fried onions: To substitute bread crumbs for the canned fried onions, pulse 4 slices hearty white bread (torn into pieces) in a food processor or blender. You will have about 3 cups of crumbs. Stir in 3 tablespoons melted butter or olive oil and fry in a large skillet over medium-high heat until browned. Sprinkle over the casserole just before serving.
  4. Yield: This recipe makes about 10 cups of casserole, enough for 10 1-cup sized, side dish (you’ll be able to feed more than 10 people depending on how many sides you have at Thanksgiving).
  5. Storage: Store leftovers covered in the refrigerator for up to 4 days.
  6. Make ahead: You can make the mushroom sauce up to 2 days before. Cool and refrigerate. Since the sauce will be going in cold, increase the crockpot time to 3 hours on HIGH or 5 hours on LOW.

Nutrition

Serving: 1cupCalories: 280kcalCarbohydrates: 12gProtein: 3gFat: 25gSaturated Fat: 14gTrans Fat: 1gCholesterol: 58mgSodium: 315mgPotassium: 207mgFiber: 1gSugar: 1gVitamin A: 632IUVitamin C: 4mgCalcium: 30mgIron: 1mg
Did you make this recipe?Tag @culinaryhill on Instagram so we can admire your masterpiece! #culinaryhill

5 from 40 votes (29 ratings without comment)

Questions and Comments

Thank you for your comments! Please allow 1-2 business days for a reply. Our business hours are Monday through Friday, 9:00 am PST to 5:00 pm PST, excluding holidays. Comments are moderated to prevent spam and profanity.

Your email address will not be published. Required fields are marked *

Recipe Rating




This site uses Akismet to reduce spam. Learn how your comment data is processed.

Comments

  1. I made this recipe to take to our family Thanksgiving get-together. It was excellent and everyone enjoyed it. My comment is about a recommendation from you in the directions. They said to microwave frozen green beans and drain them well. my complaint / suggestion for the future is to NOT use a salad spinner to spin them dry if you buy French Cut Green Beans!. Using the salad spinner probably would be fine for regular cut beans.
    However, lots of the small pieces of the French Cut Beans got trapped in the tiny openings of the salad spinner. They did not even rinse out!
    I finally had to use a tweezer to get them all out, which took almost an hour!5 stars

    Reply

    1. Hi Sherri, I’m glad everyone enjoyed the recipe! As for the salad spinner, I’m so sorry that happened to you. I’ve never run into this issue but thank you for the warning in case any other readers run into the same problem. – Meggan

  2. I will be making this on Thursday but for a smaller group. If I’m using 1 lb of fresh green beans and cutting the recipe in half, would it cut the cooking time in half?

    Reply

    1. Hi Debra, great question! The cooking time likely would be less, depending on what size slow cooker you use. I usually make this in a 6-quart slow cooker, but if I were going to do a smaller batch, I would use a smaller slow cooker so the cooking times would be closer to the recipe. Slow cookers’ power and sizes vary so much. I would keep an eye on it, and turn it to warm to hold until you’re ready to serve. Enjoy! – Meggan

  3. I have never made a green bean casserole before. This recipe sounds good. I would like to use fresh green beans. How many pounds do you recommend for your recipe?

    Reply

    1. Hi Julie, I’m so sorry that I didn’t have that information in the recipe! I was actually shocked, I have all this information about HOW to substitute fresh green beans, but not HOW MANY fresh green beans to use! So silly. It’s 2 pounds of fresh green beans, that’s what you want. I’m so sorry about that! Also, after you trim the fresh green beans, I recommend cutting them in half (not lengthwise, just like chopping them in half so they are the same size as frozen beans). Good luck and sorry again! I’m going to go add that to the post right now. -Meggan

  4. Meggan,
    Reviewing your recipe I noticed no fried onions rings were mixed in with the beans and the sauce. Is this because they get toooo mushy and better to just put on top just before serving? Also, if I do that would it be best to put the casserole from the slow cooker in the oven and toast the onions for about 10 minutes at 350?

    Thanks….Beverly
    P.S. Loved your mother’s comment….I grew up in the midwest and my mother always said the same thing……6 of 1…half a dozen of the other

    Reply

    1. Hi! Yes! Your thoughts are exactly right. They would get too mushy (for my liking anyway)! You can absolutely bake it longer to toast the onions, I just never have room in my oven for that, and I think they’re fine as is. I sometimes even sneak hand fulls out of the can! 🙂 Happy Thanksgiving Beverly!

  5. Hello! Thanks for the recipe. Can’t wait tio try it. I was just wondering what size crock pot you are using and if I increase servings to 20 people, will a 6 qt crockpot work? Thank you!

    Reply

    1. Hi Jennifer, you should be fine with this, but it may be close. I would definitely recommend mixing the green beans in the mushroom sauce in a very big bowl AND THEN add it to the crock pot. I think it might just get messy if you try to do all the mixing in the crock pot. If they don’t all fit, you can always store the remaining in the fridge and bake them (but who has oven space for that). I added the baking instructions to the recipe card a few days ago because someone else requested it. Hopefully it works for you- fingers crossed! -Meggan

    1. Hi Laura, yes definitely! I had adapted this from a Cook’s Illustrated recipe to make the slow cooker version, but their recipe was originally made in the oven. Everything is the same through the part where you toss the beans in the sauce. Then, instead of transferring that to a slow cooker, spread it in the bottom of a 3-quart OR a 9×13 baking dish. Sprinkle with the topping and bake at 425 degrees until the top is golden brown and the sauce is bubbling around the edges, about 15 minutes. I hope this helps! Thank you! -Meggan

  7. We will be traveling 4hours to our destination on the day before Thanksgiving. I plan on making the mushroom sauce and thawing the beans ahead of time. Would it be best to assemble the casserole or put it in separate containers and then assemble it Thanksgiving morning? Also, I will be doubling the recipe…..will I need more cooking time?

    Thanks for your help…..Happy Thanksgiving!
    Beverly5 stars

    Reply

    1. Hi Beverly, it doesn’t really matter if you assemble it ahead of time or not. As my mom would say – 6 of 1, half a dozen of the other. I would say if you want to transport it unassembled, you could leave the beans frozen (they will thaw on the way). You’ll need a cooler either way unless everything is frozen solid.

      As for doubling the recipe… I’ve only tripled it, not doubled it. Here are the instructions for tripling. What you’ll need to do will fall somewhere between this and the original. The actual SLOW COOKER time isn’t increased, just the ingredients for making more sauce.
      Cook the mushrooms for about 10 minutes in Step 2 and simmer the sauce for 10 minutes in Step 3. Cook on HIGH for 2 hours or LOW for 4 hours (or until a thermometer reaches at least 165 degrees in the middle of the casserole). Add more canned onions throughout serving time if the top layer is depleted, if desired.

      I hope this is helpful! If you need more info, just let me know. Thanks! -Meggan

  8. Just made over the holidays for a family dinner…..I love using the crockpot (and liners) to help with clean up at the end and to not have too many things going on around meal time. Everyone, including the little ones, was a fan and it was gone by the end of the night. I mixed in some of the fried onions into the green beans ahead of time and let them all cook and get comfy together. PERFECT. 5 stars

    Reply

  9. Can you double this recipe? I think the tripled version is going to be too much, but since it requires some changes to the recipe, I’m curious if that goes for doubling too. I’ve only ever made the single version and love it!!!

    Reply

    1. Hi Ellen – YES! I’ve doubled it and it still fit in my crockpot. And it was amazing. Feel free to mix in more of the fried onions too – that’s what I did. 😀 Happy Thanksgiving! -Meggan

  10. So I came across this recipe because I was looking at making cream of mushroom from scratch. You have a recipe for condensed cream of mushroom that is slightly different than this recipe calls for. It seems the condensed soup you made has a bit more depth to it. Would I just add water to that one and substitute it for what is in this one? What are you recommendations? Thanks in advance.5 stars

    Reply

    1. Hi Chris! Yes, this recipe is basically the cream of soup in the un-condensed version. I think (but maybe I’m wrong) that if you make traditional green bean casserole, you would add some sort of liquid to it to thin out the canned cream of soup. So my recipe basically factors that in. But in the event that I’m wrong, or you just want to use the condensed version, I would make the sauce with the condensed soup and just see what you think. Make it, taste it, throw it all together, if it seems too thick you could add water, chicken stock, milk, whatever you want. Does that make sense? I’d make it and go with your gut, literally and figuratively. I hope this helps. If you have other questions just let me know! -Meggan