Slow Cooker Green Bean Casserole Recipe

Green bean casserole is a classic American side dish, especially popular on the table at Thanksgiving celebrations every year. All these ingredients are inexpensive and easy to find, and the best part is, after very minimal prep time, the slow cooker does the bulk of the work. Serve this up alongside some turkey or a roasted chicken.

This recipe is brought to you by Laura Sampson, a recipe developer, food photographer, blogger, and mother of three, living in Palmer, Alaska. When we asked her what inspired this popular side dish in slow cooker form, she said, "I always run out of oven room on Thanksgiving. I'm usually cooking for a crowd. I am always putting too much in my oven. It doesn't cook as well as it should. It doesn't bake right, the turkey won't roast... you can easily make green bean casserole in the slow cooker and you can plug that in anywhere. It doesn't have to be in your kitchen taking up space. It can be on a buffet, a side table, anywhere."

While this slow cooker green bean casserole is a Thanksgiving treat, Sampson's blog, Little House Big Alaska, serves up all kinds of fun baking and cooking recipes, all year long. 

Before you start any meal, it's best to get all the ingredients ready to go on the counter, so you've got what you need for each step, and aren't delayed because you're frantically searching the pantry. For this slow cooker green bean casserole, the components are really simple. In addition to the slow cooker, you'll need frozen green beans. Sampson likes frozen ones, mainly because they're easier to find and less fuss, but fresh is certainly usable too. "Fresh would be great," she says. "I don't usually get fresh because they're harder to come by, and honestly frozen green beans are always cleaned and ready to go, so it cuts out the picking off the ends."

For the cream of mushroom soup, it doesn't necessarily have to be Campbell's brand but Sampson does reiterate the importance of using condensed soup, as opposed to ready-to-eat. She explains, "...you're thinning it down with milk so if you bought one of the ready-to-serve soups, it would be a different consistency."

You'll also need evaporated milk, salt, and crispy fried onions. Put the green beans in a large bowl but have a smaller bowl on hand for holding the other ingredients while you mix them together.

Once you've got them all gathered the next step in prepping ingredients is securing the proper measurements for each one. Again, part of a successful recipe execution is having what you need, and in the proper quantity, ready to go. 

Place the pound and a half of frozen green beans in a relatively large mixing bowl (large enough so that you won't have a ton of spillage when you coat the beans with the soup-milk-onion combo). Then measure out 3/4 cup of the evaporated milk and one and 1/3 cup of the crispy onions — but leave the rest of crispy onions on the counter, you'll be doling more of those out at at various stages of this recipe. You'll be using the entire 10.5-ounce can of condensed soup so just open the can and set it aside. The recipe calls for a teaspoon of salt but more or less can be utilized, depending on your taste. 

Now for the science-experiment-y portion of the recipe. In a small bowl, you'll combine the cream of mushroom soup, the evaporated milk, and the salt. Use a whisk (and if you're wondering, there are lots of tricks of the trade when it comes to using a whisk) to thoroughly mix these ingredients together, and don't skimp on the thorough mixing. This mixture will serve as the liquid base for the whole casserole. 

You might be asking yourself (we were), why evaporated milk? It's become a go-to for Sampson over the years with certain recipes. "It has a tendency not to curdle like fresh milk can... whenever I've gonna be cooking milk at a high temperature, I prefer evaporated milk," she says. If the recipe calls for the milk to be bubbling and hot, it probably needs to be the evaporated kind.

Now it's time to add in the first batch of crispy fried onions. After you've mixed the soup, milk, and salt thoroughly together, you'll need to stir in 2/3 cup of the crispy fried onions. It's important to note in this step, the liquid-salt mixture should always be well-combined before you stir in the onions, which Sampson recommends doing with a small wooden spoon. 

When asked why this is the protocol for this slow cooker green bean casserole, Sampson explains that it's important the onions don't get "pulverized" in the process of putting together the casserole. They should be carefully folded into the liquid mixture once the heavy duty mixing is done. Basically, you just don't want to crush those onions in this part of the recipe because we need them to stay as fully formed as possible, and crunchy too. So stir the soup and milk, then add the onions. Got it? 

Now it's time to combine the frozen green beans with the soup, milk, salt, and onions, in preparation for go-time on the slow cooker. Carefully pour the mixture of cream of mushroom soup, evaporated milk, salt, and crispy fried onions over the bowl of green beans. Then you're going to thoroughly coat the green beans with the soup mixture, making sure every inch of every bean is properly covered. A spatula or that wooden spoon from the previous step should be able to do the trick for this. 

You want to make sure all the beans are drenched in the mixture, so you've got a uniform taste in every bite of this delicious green bean casserole. Again though, try to be mindful of not completely crushing the crispy onions as you carry out this step. Some breakage is okay but again, we don't want them totally pulverized.

Now the fun part: pour the coated 'n covered green beans into the slow cooker. Then bust out the crispy friend onions stash because before you put on the lid to cover the cooker, you're going to sprinkle another 1/3 cup of the crispy onions over the top.

You may be wondering what size slow cooker you need for this recipe. In terms of size, slow cookers do have a lot of varieties so it can be confusing. Sampson uses a 4-quart size slow cooker. If you have something smaller or larger, keep that in mind when you're calculating the cooking time. She notes, "...if you use a smaller slow cooker, it's probably going to take more time because it's going to be deeper, whereas if you use a bigger one and it's very spread out on the bottom and it's thinner, it will cook probably faster." This is definitely something to keep in mind when preparing this slow cooker green bean casserole.

This is your time to get to work on another dish you're serving with the meal — or binge watch the television show of your choice. Cook the green bean casserole in the slow cooker on high for three hours, or until the green beans are "done." How can you tell when the green beans are done? Sampson has a system for this. "I actually open it, use a fork, pull one out," she says. "Does it feel tender? Is it cooked through? Frozen or fresh green beans are not quick like canned green beans...they actually take longer." 

Just remember that each time you open that slow cooker, you let out all of the hot air it worked so hard for and you're adding on more cooking time. Wait at least three hours and until the mixture looks bubbly and ready to eat before you give it a test.

It's also really important to remember the cooking time can also vary based on what kind of slow cooker you have. Sampson insists, "Before you serve this to guests, make it in advance, see how long your brand takes because they all cook at different rates."

When the green bean casserole is finished cooking, you can change the setting of the slow cooker to "warm" and let it sit until you're ready to serve it. Yet another huge perk of the slow cooker life. Not all slow cookers have the "warm" setting, however. Sampson still recommends, "I would say "keep warm" if you have that option... a lot of old slow cookers don't have that options but if it does, I like that option because it just keeps it warm enough to serve..."

If your slow cooker doesn't have a warm setting, be careful just switching the setting to "low." You don't want to risk over cooking or worse, burning, this fab slow cooker green bean casserole. Nobody wants burnt green beans on Thanksgiving, unless of course they were looking for an excuse to avoid vegetables at all costs.

This last step is optional but it does make for a pretty presentation. When the green bean casserole is ready to eat, you can transfer it from the slow cooker to a casserole or other serving dish. Just be sure to sprinkle the remaining crispy fried onions over the top of it, either in the serving dish or in the slow cooker, if you're planning to just dole it out from there (there is no shame in a "the less dishes, the better" game). 

Sampson likes a legit serving dish and claims, "You can serve it from the crock...just not gonna be as pretty as having it in a beautiful dish...that small rectangular [seen in the photo here] one is a 2-quart and that fit pretty well...and then I had some round small, little crocks that we sometimes use for serving...and they're like a cup and a half; it's probably more than a single serving but it looks cute." There is nothing wrong with making sure the food you serve is both tasty and cute.

Now it's time to eat! We asked Sampson if she had any recommendations for what to serve this slow cooker green bean casserole with (besides the Thanksgiving turkey, of course), and she suggests, "Serve it with a fork!" Good call; a fork does seem like the best utensil for consuming this delight. She also adds that this green bean casserole is "great with leftovers...[such as]... leftover sliced ham, chicken or turkey..." Do not serve it with casserole though. Sampson says that's a definite no-go.

When asked for any further tips, her final thought just reemphasizes the "know your slow cooker" mantra mentioned earlier. "Make a slow cooker recipe beforehand so you're not in a bind on Thanksgiving when your slow cooker takes six hours rather than three like mine," she says. This is probably a good tip for cooking in general: know thy appliances, and always test the recipe before you serve it to a large group of hungry people.