This Vegan Green Bean Casserole recipe features tender green beans and mushrooms in a creamy sauce, topped with crispy onions. You’ll love this homemade healthy side dish infused with green beans and the ultimate creamy mushroom filling!
Green Bean Casserole From Scratch
Even though I grew up preferring green beans from a can, somewhere along the way, I found out how much I loved fresh green beans steamed with olive oil and garlic. And then I decided to try fresh green beans in this casserole.
There’s nothing like tender green beans served with the ultimate creamy, cheesy mushroom filling and topped with crispy fried onions.
Of course, making it homemade can take a little more time. However, I have a trick to make this recipe go a lot faster.
Why This Recipe is a Winner
- Using frozen green beans produces a “bursting with fresh” flavor while keeping this recipe easy to make
- Making homemade fried onions keeps this recipe vegan and egg-free, while also producing crispy onions used as a topping and in the casserole
- Vegan cheddar shreds add a delicious cheesy sauce to the filling, making every bite worthy of another one!
What You Need
You can find the full printable recipe, including ingredient quantities, below. But first, here are some explanations of ingredients and steps to help you make this recipe perfect every time.
Here are the ingredients you’ll need for this recipe:
- Fried Onion Batter — We’ll make a batter for the fried onions that consist of plant-based milk, apple cider vinegar, flour, salt, and pepper.
- Onion — I prefer a yellow onion because they’re sweeter once cooked.
- Flour — I recommend all-purpose flour. You can substitute gluten-free flour but be prepared that the fried onions may not fry up as golden as when using all-purpose flour.
- Vegetable oil — I used canola oil.
- Vegan butter — Any vegan butter should do, such as Earth Balance.
- Portobello mushrooms
- Vegetable Bouillon — I love using Better than Bouillon No Chicken Base or the Vegetarian base because it creates a high-quality broth.
- Vegan cheddar shreds — I use either Daiya or Follow Your Heart Cheddar Shreds.
- Frozen green beans — You can use fresh, but I like the fresh-like flavor of frozen, and it comes already chopped, which is nice!
- Vegan parmesan cheese — You can buy this at health food stores or make your own vegan parmesan.
How to Make Vegan Green Bean Casserole
There are a few steps to making this delicious casserole, but I’ll share with you some time-saving tips too!
- Fried Onions. Marinate the onions in vegan buttermilk, then coat in a flour mixture and fry them in a skillet using vegetable oil. Be sure to save any leftover flour and milk from this step!
- Make the Cheesy Sauce. Melt butter in a skillet and add the mushrooms and cook until they’re nice and tender. Next, add some garlic, and cook for about a minute. We’ll combine the leftover buttermilk and flour from the fried onions and add that to the skillet. Watch and stir as it transforms into a delicious sauce!
- Add Green Beans. Add the frozen green beans to the skillet, stirring to coat them. Bring that to a simmer and add the vegan cheese. Cook until the cheese melts and then stir in some of the fried onions (reserving plenty for the topping).
- Bake. Transfer the contents from the skillet to a casserole dish and top with the rest of the fried onions and some vegan parmesan. Then bake at 375°F for 20 minutes, until the sides are bubbly and the onions are golden brown.
How to Make Fried Onions
I recommend marinating onions in a mixture of plant-based milk and apple cider vinegar (basically, vegan buttermilk) for 20–30 minutes prior to frying them. You can even soak them overnight.
This marinade helps soften the onion flavor and the buttermilk mixture will help the flour coating stick to the onions.
Gluten-Free Fried Onions
You can use gluten-free flour to make gluten-free fried onions, but I find that the flour doesn’t brown as much. To help gluten-free fried onions turn a more golden color, coat the top of the fried onions (immediately before baking) with a mixture of 1 tablespoon melted vegan butter with 1 teaspoon agave nectar.
To make a gluten-free green bean casserole, use quality gluten-free baking flour in the sauce.
Air Fryer Fried Onions
To make air fryer fried onions, follow the steps above to prepare the onions. When they’re ready, set the air fryer temperature at 375°F and fry the onions for 10–15 minutes. Depending on the size of your air fryer, you may need to cook the onions in batches.
When air frying, be sure to remove the basket and toss the onions a couple of times during cooking.
Can you make green bean casserole ahead of time?
It’s easy to make green bean casserole ahead of time by preparing the casserole as directed. Then cover and refrigerate the casserole for up to 3 days. When you’re ready to serve, bake it for 20 minutes in the oven at 375°F.
Can you freeze green bean casserole?
Green bean casserole can be frozen for up to 3 months. Transfer the casserole to a freezer-safe container and place it in the freezer. The day before you’re ready to serve it, transfer it to the fridge to thaw overnight. Then bake it at 375°F for 20–30 minutes.
Is green bean casserole healthy?
You may already know this, but green beans are healthy. The green color gives it away. So, it’s the things added to green beans that cause a dish like green bean casserole to tip on the scale towards unhealthy. The main culprit? Fried onions. You can bake your fried onions or make them in an air fryer to help make this casserole healthy.
Vegan Thanksgiving Recipes
I hope you love this vegan green bean casserole as much as we do!
Vegan Green Bean Casserole
For the French fried onions:
- 1 cup plant-based milk (plain, not vanilla)
- 1 teaspoon apple cider vinegar
- 1 medium onion peeled and sliced into thin rings
- ¾ cup all-purpose flour
- ½ teaspoon salt
- ¼ teaspoon black pepper
- 4 tablespoons vegetable oil
For the Casserole:
To Make the Fried Onion Topping:
- In a medium-sized bowl stir together the milk and vinegar. Add onion rings and use a spoon to stir and coat them. Set aside for onions to marinate for approximately 30 minutes.
- On a large plate, stir together flour, salt, and pepper.
- Use tongs to pull a small batch of the onions from the milk mixture, dangling them over the bowl to let excess liquid drip off. Transfer the onions to the flour mix. Repeat until all onions have been transferred. Use tongs to toss and coat. Reserve the milk mixture for the casserole.
- Cover a plate with 2–3 paper towels. Heat 1 tablespoon oil in a large skillet over medium heat. Once the oil is heated, add some of the battered onions in an even layer across the pan with minimal overlapping. Cook 2–3 minutes and use tongs to gently toss. Cook for 2–3 minutes again and then toss again. The onions should begin to turn a golden brown and become crispy on the edges. Transfer cooked onions to a paper towel-lined plate. Repeat this step with the remaining onions.
For the Green Bean Casserole
- In a skillet over medium heat, add vegan butter. Heat up the oil then add the mushrooms and cook until tender, about 3 minutes. Add minced garlic. Stir and cook for about 30 seconds.
- Combine the milk mixture from the onions above, with 1 cup water, and bouillon. Stir to combine. Use any leftover flour from the fried onions and add 3 tablespoons flour to the milk mixture. Stir to remove any lumps. Pour this over the contents in the skillet and stir to combine.
- Add the green beans, stir to coat, and then bring it to a simmer. Add vegan cheese and stir until it melts. Then reduce heat to medium-low and cook for approximately 5 minutes, until the green beans are no longer frozen and slightly tender, but still a little crisp and the sauce has thickened. If the sauce does not thicken, sprinkle another tablespoon of flour over the top and use a spatula to stir it in.
- While the green beans simmer, preheat oven to 375°F.
- Pour the green bean mixture into a 9" square baking dish or casserole dish. Add about 1/2 of the fried onions and stir them throughout. Equally, distribute remaining fried onions over the top. Sprinkle with vegan parmesan. Bake for 20–25 minutes.
- When done, remove from oven and set aside to cool for 5–10 minutes before serving. Cover and refrigerate any leftovers not eaten right away. These will keep in the fridge for up to 5 days.
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- Make-ahead Tips: Prepare the green bean casserole ahead of time, including baking. Allow it to cool to room temperature and then cover and refrigerate. To serve, remove from the fridge and let it sit until it is room temperature then reheat in the oven at 375°F for 15 minutes
- Fried Onions. Most store-bought Fried Onions are vegan as well, so you can substitute store-bought onions if you prefer to skip frying them yourself.
- Mushrooms: You can leave out the mushrooms if you prefer.
- Vegan Cheese: I used Daiya cheddar shreds, but Follow Your Heart cheddar shreds could work here too.
- Double the recipe: It’s easy to double this recipe. Simply use double the ingredients and transfer to a larger casserole dish, such as a 9X13. Top with fried onions, then bake, around 25 minutes, until bubbly around the edges.
The nutrition information shown is an estimate provided by an online nutrition calculator and should not be considered a substitute for a professional nutritionist’s advice.