Vegetarian French Onion Soup Recipe

Vegetarian French onion soup is all about comfort and rich flavors in one hearty bowl! Caramelized onions infuse the broth with a sweet-savory depth, while the crunchy piece of baguette and gooey, melted Gruyère cheese on top bring everything together. It’s the perfect dish to serve on cold evenings!

A Note From Kristen

If you love delicious dishes with simple ingredients, this is one recipe you’ll want to try! I worked hard to develop a vegetarian version that rivals the traditional beef broth versions, and the flavor is just as rich and layered. It’s one of my go-tos when entertaining non-vegetarian friends, and it’s so rewarding to watch them savor every spoonful. This soup is classic proof that vegetarian food can be just as deeply filling and satisfying!

~Kristen

A bowl of vegetarian French onion soup topped with melted cheese and bread, with a spoon inside, placed on a gray cloth napkin.

Ingredient Notes

Please keep in mind that this is just a quick overview. Visit the full recipe for amounts and instructions!

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Unsalted Butter: Coats the onions as they caramelize, helping create a smooth, rich base with a silky mouthfeel.
Extra Virgin Olive Oil: Adds its own subtle flavor to the mixture and helps prevent the butter from burning during the slow cooking process.
Yellow Onions: The heart of the recipe! Their natural sugars caramelize while cooking, giving the French onion soup its deep, complex taste.
Salt: Enhances the natural flavors of the dish. It also helps the onions soften and caramelize more evenly by drawing moisture from them as they cook.
Ground Black Pepper: Adds gentle warmth and spice that complements the sweetness of the onions.
Fresh Thyme Leaves: Infuses the soup with herbal notes that make the flavors more layered and lively. You can also use dried thyme leaves if that’s what you have.
All-Purpose Flour: Helps give the soup body and richness. Use gluten-free flour if necessary.
Dry White Wine: Adds brightness and subtle acidity that keeps the soup from being too heavy. You can also use apple cider vinegar + vegetable broth mixture to keep the recipe alcohol-free.
Vegetable Broth: Acts as the main liquid base that carries the depth of flavor of onions while also making the dish feel hearty, even without meat. Use a homemade or high-quality store-bought for best results.
Tamari or Soy Sauce: Deepens the umami flavor and enriches the soup with its subtle saltiness. Use gluten-free if necessary.
Bay Leaf: Helps give the dish a rounder, more developed taste.
Baguette: Acts as a crunchy, sturdy base that soaks up the flavorful broth and carries the melted cheese topping. Use gluten-free bread if necessary. My favorite gluten-free baguette is made by Schar!
Grated Gruyère or Dairy-Free Cheese Alternative: Melty cheese creates a golden, cheesy, bubbly crust that defines vegetarian French onion soup. Use rennet-free Gruyère if vegetarian. My favorite vegetarian (rennet-free) Gruyère comes from Whole Foods (their 365 brand).

A bowl of vegetarian French onion soup topped with melted cheese and toasted bread sits on a wooden surface, with a spoon resting inside. A folded striped napkin is beside the bowl.

How to Make Vegetarian French Onion Soup

01

COOK ONIONS

Melt the butter with olive oil in a large pot over medium-low heat. Add the onions and salt, cooking slowly for 30–40 minutes, stirring often, until rich and golden brown.

Sliced onions cooking in oil in a pan, stirred with a blue spatula—the perfect start for a delicious vegetarian French onion soup.

02

ADD

Stir in the thyme, pepper, and flour, and cook for about 1 minute to blend the flavors.

A blue spatula mixing cooked onions and powder in a white pan with some oil, the perfect base for vegetarian French onion soup.

03

DEGLAZE

Deglaze the pot with white wine or the vinegar-broth mixture, scraping up any browned bits. Let it simmer until the liquid is mostly reduced.

A blue spatula stirs caramelized onions in a white pan, creating a golden, saucy mixture perfect as the base for vegetarian French onion soup.

04

ADD BROTH

Stir in the vegetable broth, tamari, and bay leaf. Bring to a gentle simmer and cook for 20 minutes, then remove the bay leaf.

A close-up of reddish-brown broth with oil droplets and a single bay leaf floating on the surface, showcasing a warm bowl of vegetarian French onion soup.

05

TOAST AND TOP

Preheat the broiler and arrange baguette slices on a baking sheet. Toast until golden on both sides. Spoon the soup into oven-safe bowls, top with a baguette slice and plenty of Gruyère, then broil until the cheese is melted and bubbling.

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White bowl of vegetarian French onion soup with shredded cheese, thin noodles, and a slice of toasted bread on parchment paper.

06

SERVE

Serve hot, garnished with a sprinkle of fresh thyme. Enjoy!

A bowl of vegetarian French onion soup topped with melted cheese and bread, with a spoon resting inside and a striped cloth napkin beside the bowl.

A bowl of vegetarian French onion soup topped with melted cheese and herbs, with a spoon resting inside, on a wooden surface.

Serving Ideas

Pair with a simple spinach and arugula salad or chickpea chopped salad.
Serve with roasted vegetables, like cabbage steaks or roasted sweet potato slices.
Pair with sandwiches or a grilled vegetable panini.
Serve alongside polenta fries with spicy sriracha aioli.
Pair with French bread, ratatouille, or your favorite protein dish.

A white bowl of vegetarian French onion soup topped with melted cheese and a slice of bread, with a spoon resting inside; another bowl and a striped napkin are nearby.

Kristen’s Top Tips

Slice the onions thinly so they cook at the same rate and break down into a consistent, jammy texture.
Don’t rush when cooking the onions! Gently cooking them allows their natural sugars to develop without burning and turning them bitter. The time it takes to caramelize them will vary slightly from stovetop to stovetop, as well as the type of pot used.
Use yellow onions for this recipe. Sweet onions may make the soup too sugary, while red onions may turn the soup muddy in color. If you want the soup to be sweeter, I recommend a blend of yellow and sweet onions.
Toasting the baguette slices ensures they hold up under the cheese melt and soup without turning soggy.
For mild flavor variations, you can try adding some cloves of garlic towards the end of caramelizing the onions. You can also switch things up by using vegan Worcestershire sauce, balsamic vinegar, dry sherry, or low sodium vegetable broth.

Two bowls of vegetarian French onion soup topped with melted cheese and toasted bread, one with a spoon resting inside.

Vegetarian French Onion Soup Recipe

Enjoy a rich, hearty, and comforting vegetarian take on classic French onion soup.

Author: Kristen Wood
Servings: 4 servings

Prep Time: 10minutes minutes Cook Time: 1hour hour Total Time: 1hour hour 10minutes minutes

Course: Appetizer, Main Course, Soup Cuisine: French Diet: Gluten Free, Vegetarian

Ingredients

3 tablespoons unsalted butter
2 tablespoons extra virgin olive oil
5 large yellow onions thinly sliced
1 teaspoon salt
½ teaspoon ground black pepper
2 teaspoons fresh thyme leaves or 1 teaspoon dried
1 tablespoon all-purpose flour use gluten free if necessary
½ cup dry white wine or 2 tablespoons apple cider vinegar + 6 tablespoons vegetable broth
6 cups vegetable broth
1 tablespoon tamari or soy sauce use gluten-free if necessary
1 bay leaf
6 slices baguette use gluten free if necessary
1 ½ cups grated Gruyère or dairy-free cheese alternative, use rennet-free Gruyère if vegetarian (see notes)

Instructions

Heat the butter and olive oil in a large pot over medium-low heat. Add onions and salt, cooking slowly for 40-50 minutes, stirring often, until deeply golden and caramelized.
Stir in the thyme, pepper, and flour, cooking for 1 minute.
Deglaze the pan with white wine if using, or add the vinegar-broth mixture, scraping up any browned bits. Simmer until mostly reduced.
Add the vegetable broth, tamari, and bay leaf, then bring to a gentle simmer for 20 minutes. Remove the bay leaf.
Preheat the broiler and arrange baguette slices on a baking sheet. Toast until golden on both sides.
Ladle the soup into oven-safe bowls, top each with a toasted baguette slice and plenty of Gruyère, then broil until cheese is melted and bubbling.
Serve hot with extra thyme sprinkled on top.
Enjoy!

Notes

My favorite vegetarian (rennet-free) Gruyère comes from Whole Foods (their 365 brand!).

Storage and Reheating

Store cooled leftover soup (without baguette or cheese topping) in an airtight container and keep it in the refrigerator for up to 4 days. You can also freeze the vegetarian French onion soup for up to 3 months.

To reheat, you can warm the soup on the stove (medium heat) or in the microwave. Stir occasionally and avoid boiling to preserve the flavors. Once hot, serve in bowls, top with toasted baguettes and grated Gruyere cheese, then broil them until golden and bubbly.

Nutrition

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Previously Published on moonandspoonandyum

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