This Vegan Green Bean Casserole is creamy, savory, and topped with crispy fried onions. The green beans stay tender with a little bite, while mushrooms give the sauce a rich flavor. It is an easy comfort-food side for Thanksgiving, holidays, or a cozy family dinner.
Servings: 8
Prep time: 20 minutes
Cook time: 35 minutes
Total time: 55 minutes
Why I Love This Recipe
Green bean casserole has always felt like one of those dishes that belongs in the middle of a big table. I wanted a vegan version that still had the creamy middle and crunchy onion topping that make the classic so good.
The key was not simply swapping out the dairy. The sauce needed enough mushroom flavor to taste rich without being heavy. Cooking the mushrooms until their extra water is gone makes a big difference. A little soy sauce also gives the sauce a deeper savory taste.
Here is what I especially love about it:
- Fresh green beans give the casserole better color and texture.
- Mushrooms make the sauce naturally rich and savory.
- Unsweetened plant milk keeps the sauce creamy without dairy.
- Crispy fried onions add the salty crunch everyone expects.
- Most of the ingredients are easy to find.
- You can prepare much of it ahead of time.
- It tastes special enough for a holiday but is simple enough for dinner.
What You’ll Need
- 1 1/2 pounds fresh green beans, trimmed and cut into 2-inch pieces
- 2 tablespoons olive oil
- 12 ounces cremini mushrooms, thinly sliced
- 1 medium onion, finely diced
- 3 garlic cloves, minced
- 3 tablespoons all-purpose flour
- 2 cups unsweetened plain oat milk
- 1 cup low-sodium vegetable broth
- 1 tablespoon soy sauce
- 1/2 teaspoon dried thyme
- 1/2 teaspoon fine salt, plus salt for the blanching water
- 1/4 teaspoon black pepper
- 2 cups vegan crispy fried onions, divided
Recipe and Instructions
Step 1: Blanch the Green Beans
Heat the oven to 375°F (190°C).
Bring a large pot of water to a boil. Add enough extra salt to lightly season the water. Add 1 1/2 pounds fresh green beans, trimmed and cut into 2-inch pieces. Cook for 4 minutes. The beans should turn bright green and begin to soften but should still have a little bite.
Drain them right away in a colander and rinse them under very cold water. Drain well. This stops them from getting too soft while the casserole bakes.
Step 2: Brown the Mushrooms and Onion
Place a large skillet over medium-high heat. Add 2 tablespoons olive oil.
Add 12 ounces thinly sliced cremini mushrooms and 1 medium finely diced onion. Cook for 7 to 9 minutes, stirring now and then. Keep cooking until the mushrooms are browned and most of their liquid has cooked away.
Add 3 minced garlic cloves and cook for 30 seconds, just until fragrant.
Step 3: Make the Creamy Mushroom Sauce
Turn the heat down to medium. Sprinkle 3 tablespoons all-purpose flour over the browned mushroom mixture. Stir constantly for 1 minute so the flour loses its raw taste.
Slowly pour in 2 cups unsweetened plain oat milk while whisking. Then whisk in 1 cup low-sodium vegetable broth.
Add 1 tablespoon soy sauce, 1/2 teaspoon dried thyme, 1/2 teaspoon fine salt, and 1/4 teaspoon black pepper.
Cook for 4 to 6 minutes, stirring often, until the sauce is thick and creamy. It should coat the back of a spoon.
Step 4: Assemble the Casserole
Put the drained 1 1/2 pounds blanched green beans into the round baking dish.
Pour all of the creamy mushroom sauce from Step 3 over them. Add 1 cup vegan crispy fried onions. Gently stir until the green beans are evenly covered.
Spread the mixture into an even layer.
Step 5: Bake and Add the Crispy Topping
Bake the casserole uncovered at 375°F (190°C) for 20 minutes.
Carefully remove it from the oven. Sprinkle the remaining 1 cup vegan crispy fried onions evenly over the top.
Return the casserole to the oven for 8 to 10 minutes, until the sauce is bubbling around the edges and the onions are crisp and golden brown.
Let it rest for 5 to 10 minutes before serving. This gives the creamy sauce time to settle and thicken.
Why This Recipe Works (Quick Science)
Blanching the green beans first starts the cooking process without making them mushy. Cooling them quickly helps them hold their bright color and firm texture.
Mushrooms contain a lot of water. Browning them until most of that water cooks away gives them stronger flavor and keeps the finished casserole from becoming watery.
The flour mixes with the oil and helps thicken the oat milk and vegetable broth. As the sauce heats, the starch in the flour absorbs liquid and makes the sauce creamy.
Adding only half of the crispy onions before baking is important. The onions inside give the casserole flavor, while the onions added near the end stay much crunchier.
Pro Tips
- Drain the beans well. Extra water can thin the creamy sauce.
- Give the mushrooms time to brown. If they are still watery, keep cooking them before adding the flour.
- Use plain, unsweetened plant milk. Vanilla or sweetened milk will change the flavor.
- Check your fried onions. Some brands may contain dairy, so look for ones labeled vegan.
- Watch the final few minutes. Crispy onions can go from golden to too dark fairly quickly.
Tools You’ll Need
- Large pot
- Colander
- Large skillet
- Wooden spoon or silicone spatula
- Whisk
- Measuring cups
- Measuring spoons
- Chef’s knife
- Cutting board
- Round 2 1/2- to 3-quart baking dish
- Oven mitts
Substitutions and Variations
- Green beans: Frozen green beans can work. Thaw and drain them very well first. Skip the blanching step.
- Oat milk: Unsweetened soy milk is a good swap. Unsweetened almond milk can also work, though the sauce may be a little less rich.
- Cremini mushrooms: White button mushrooms work well.
- Soy sauce: Use tamari for a gluten-free option.
- All-purpose flour: A gluten-free all-purpose flour blend can work for a gluten-free version.
- Crispy onions: Use certified vegan and gluten-free crispy onions when needed.
- More herbs: Add a little fresh rosemary or sage for a stronger holiday flavor.
Make Ahead Tips
You can blanch the beans and make the mushroom sauce up to 1 day ahead. Mix the beans, sauce, and first cup of crispy onions in the baking dish. Cover and refrigerate.
For the crunchiest result, keep the final cup of crispy onions separate.
When ready to cook, let the cold baking dish sit out while the oven heats. Bake until the center is hot and bubbling, which may take a few extra minutes. Add the final crispy onions near the end as directed.
Common Mistakes
- Overcooking the beans: Remember that they cook once in the water and again in the oven.
- Not browning the mushrooms: Watery mushrooms can lead to thin sauce and weaker flavor.
- Adding plant milk too fast: Pour it in slowly while whisking to help prevent lumps.
- Using sweetened plant milk: Always choose plain and unsweetened.
- Adding all the onions at the start: The top will lose much of its crunch.
- Serving right away: Resting for 5 to 10 minutes helps the sauce thicken.
What to Serve With
This casserole fits right into a holiday meal, but you do not have to wait for a holiday. Try it with:
- Vegan lentil loaf
- Roasted potatoes
- Garlic mashed potatoes
- Stuffing
- Maple-roasted carrots
- Roasted sweet potatoes
- Cranberry sauce
- Vegan gravy
- A simple green salad
- Warm dinner rolls
Macros Information
Approximate nutrition per serving, based on 8 servings:
- Calories: about 220
- Protein: about 6 g
- Carbohydrates: about 27 g
- Fat: about 11 g
- Fiber: about 4 g
These numbers are estimates. The exact macros will change depending on the oat milk, vegetable broth, and crispy fried onions you use.
Leftovers and Storage
Let leftovers cool, then put them in an airtight container or cover the baking dish well. Keep them in the refrigerator for up to 4 days.
For the best texture, reheat the casserole uncovered in a 350°F (175°C) oven until hot. You can add a small handful of fresh crispy onions before reheating to bring back some crunch.
The microwave works for individual portions, but the onion topping will become softer.
Freezing is possible, but it is not my first choice. The creamy sauce and green beans can change texture after thawing.
FAQ
Q: Can I use canned green beans?
A: Yes. Drain them very well and skip the blanching step. Because canned beans are already soft, the final casserole will have a softer texture.
Q: Can I use frozen green beans?
A: Yes. Thaw them completely and drain away as much water as possible before mixing them with the sauce.
Q: What plant milk works best?
A: Unsweetened plain oat milk gives the sauce a nice creamy texture. Unsweetened soy milk is also a good choice.
Q: Why is my casserole watery?
A: The beans or mushrooms may have held too much water, or the sauce may not have cooked long enough. Drain the beans well, cook the mushroom liquid away, and let the sauce thicken before assembling.
Q: How do I know when the sauce is thick enough?
A: Dip a spoon into it. The sauce should coat the back of the spoon instead of running off like milk.
Q: Can I make this gluten-free?
A: Yes. Use gluten-free all-purpose flour, tamari instead of regular soy sauce, and certified gluten-free crispy fried onions.
Q: Can I double the recipe?
A: Yes. Use two baking dishes rather than packing everything into one very deep dish. This helps the casserole heat evenly and gives you more crispy topping.
Final Thoughts
This Vegan Green Bean Casserole keeps everything that makes the classic so comforting: tender green beans, creamy mushroom sauce, and plenty of crispy onions on top. The homemade sauce takes a few extra minutes, but that rich mushroom flavor is worth it.
Serve it warm, scoop it straight from the baking dish, and do not be surprised if that crunchy topping disappears fast. If you make it, leave a comment and share how it turned out or any questions you had along the way.