This Vegetarian French Onion Soup Recipe swaps the traditional beef broth for a rich vegetable and mushroom broth, without losing any of the deep, caramelized flavor that makes French onion soup so beloved.
Sweet onions cook low and slow until they turn a deep amber, then simmer in a savory broth spiked with dry sherry and fresh thyme.
A thick slice of toasted baguette and a blanket of melted Gruyere cheese finish each bowl under the broiler.
If you love the classic beefy version too, my French Onion Soup Recipe is a great place to start, but this vegetarian take holds its own at the table.
| Quick Recipe Summary | |
|---|---|
| Prep Time | 20 minutes |
| Cook Time | 1 hour 10 minutes |
| Total Time | 1 hour 30 minutes |
| Servings | 6 servings |
| Difficulty Level | Easy to Moderate |
Why You’ll Love This Vegetarian French Onion Soup Recipe
This soup proves that you do not need beef broth to get that deep, savory flavor everyone loves about French onion soup.
A splash of dry sherry and a spoonful of vegetarian Worcestershire sauce bring the same rich backbone.
It also happens to be a fantastic make-ahead meal, since the base only gets better after a day or two in the fridge.
Another favorite in the same cozy vein is my Slow Cooker French Onion Soup Recipe, if you would rather let a crockpot do the work.
- Deep, caramelized onion flavor without any beef broth
- Ready with mostly pantry staples and one trip to the cheese counter
- Freezer-friendly base that reheats beautifully
- A showstopping starter or light meal, especially with a side salad
- Naturally vegetarian and easy to adapt for vegan diets
Ingredients
Most of what you need is already in your kitchen, aside from a few specialty items that really make this soup sing.
Below is everything you will need to make this Mushroom Soup Recipe inspired broth base along with the classic cheesy topping.
- 4 tablespoons unsalted butter
- 1 tablespoon olive oil
- 3 pounds yellow onions, thinly sliced (about 6 large onions)
- 1 teaspoon salt, plus more to taste
- 1/2 teaspoon sugar (helps the onions caramelize)
- 3 cloves garlic, minced
- 2 tablespoons all purpose flour
- 1/2 cup dry sherry or dry white wine
- 6 cups vegetable broth
- 2 cups mushroom broth (or extra vegetable broth)
- 2 bay leaves
- 4 sprigs fresh thyme, plus more for garnish
- 1 tablespoon vegetarian Worcestershire sauce
- 1/2 teaspoon black pepper
- 1 baguette, sliced into 1/2 inch rounds
- 2 cups shredded Gruyere cheese
- 1/2 cup grated Parmesan cheese, optional
Kitchen Equipment Needed
A heavy pot is the real secret to good caramelized onions, since it holds heat evenly and does not scorch.
Read Also: Air Fryer Garlic Bread Recipe if you want another way to use up the rest of that baguette.
- Dutch oven or other heavy bottomed pot
- Mandoline slicer, for evenly thin onion slices
- Broiler safe soup crocks or oven proof bowls
- Sharp chef’s knife
- Wooden spoon
- Ladle
- Baking sheet
Recommended Products for This Recipe
These are a few products I personally reach for whenever I make this soup, based on plenty of trial and error in my own kitchen.
1. Mandoline Slicer
Slicing three pounds of onions by hand takes forever and rarely comes out even.
A mandoline gives you consistent, paper thin slices that caramelize at the same rate, so you get a smoother, more uniform texture in the finished soup.
2. Enameled Cast Iron Dutch Oven
This soup lives or dies on how evenly the onions cook, and a heavy enameled Dutch oven distributes heat far better than a thin stockpot.
It also transitions easily from stovetop to a low oven if you want to finish the caramelizing hands off.
3. Broiler Safe Stoneware Soup Crocks
Part of the fun of French onion soup is that classic bistro presentation, with cheese bubbling right over the rim of the bowl.
These crocks are built to go straight under the broiler without cracking, which is not something every bowl in your cabinet can handle.
4. Aged Gruyere Cheese
Pre-shredded cheese is convenient, but a block of real aged Gruyere melts smoother and has a nuttier, more complex flavor that makes a real difference here.
I like to buy a wedge and grate it myself right before broiling.
My Potato Leek Soup Recipe uses a similar heavy pot approach if you are looking to get more use out of your new Dutch oven.
Step-by-Step Instructions: How to Make Vegetarian French Onion Soup
Take your time with the onions here, since that slow caramelizing step is what builds all the flavor in this soup.
Another cozy, low and slow project worth trying afterward is my Roasted Cauliflower Soup Recipe.
1. Slice and Prep the Onions
- Peel 3 pounds of yellow onions and slice them thinly and evenly, about 1/8 inch thick, using a sharp knife or a mandoline slicer.
- Try to keep the slices roughly the same thickness so they cook at the same rate.
- Mince the garlic cloves and set them aside along with the sliced onions.
2. Caramelize the Onions
- Melt the butter with the olive oil in a Dutch oven over medium heat until the butter is foaming but not browned.
- Add all of the sliced onions to the pot along with 1 teaspoon of salt and the sugar, then stir well to coat every slice.
- Cook the onions, stirring every few minutes, for about 15 minutes until they soften and begin to release their liquid.
- Reduce the heat to medium low and continue cooking for 35 to 45 minutes, stirring occasionally and scraping up any browned bits from the bottom of the pot.
- If the onions start to stick or the pan looks dry, add a splash of water or vegetable broth to loosen everything up.
- The onions are ready when they turn a deep golden brown and smell sweet and caramelized, not raw or sharp.
3. Build the Broth Base
- Add the minced garlic to the caramelized onions and cook for 1 minute, stirring constantly so it does not burn.
- Sprinkle the flour over the onions and stir well to coat, then cook for 2 minutes to remove the raw flour taste.
- Pour in the dry sherry, stirring and scraping the bottom of the pot to deglaze it, and let it simmer for 2 to 3 minutes until slightly reduced.
- Add the vegetable broth, mushroom broth, bay leaves, thyme sprigs, vegetarian Worcestershire sauce, and black pepper.
4. Simmer the Soup
- Bring the soup to a gentle boil, then reduce the heat to low so it simmers softly.
- Cover the pot partway and let the soup simmer for 25 to 30 minutes, stirring occasionally, so all the flavors meld together.
- Taste the soup and adjust the seasoning with more salt and pepper as needed.
- Remove and discard the bay leaves and thyme sprigs before serving.
5. Toast the Baguette Slices
- While the soup simmers, preheat your oven broiler and line a baking sheet with the baguette slices in a single layer.
- Broil the bread for 1 to 2 minutes per side, watching closely, until both sides are lightly golden and crisp.
- Set the toasted baguette slices aside until you are ready to assemble the bowls.
6. Assemble and Broil the Soup
- Ladle the hot soup into broiler safe soup crocks or oven proof bowls, filling each about three quarters full.
- Top each bowl with 1 or 2 toasted baguette slices, arranging them so they mostly cover the surface of the soup.
- Sprinkle each bowl generously with shredded Gruyere cheese, and add a little Parmesan on top if using.
- Place the bowls on a baking sheet and broil for 2 to 4 minutes, watching constantly, until the cheese is melted, bubbly, and lightly browned.
- Carefully remove the bowls from the oven, since the crocks and soup will be very hot, and let them cool for a couple of minutes before serving.
Tips for The Best Vegetarian French Onion Soup
A few small details make the difference between a good bowl of this soup and a great one.
My Tomato Soup Recipe follows some of the same low and slow principles if you want another cozy soup to compare notes with.
- Do not rush the caramelizing step, since low and slow heat is what builds real flavor in the onions
- Use a wide, heavy bottomed pot so the onions have room to spread out and brown evenly
- Deglaze with a splash of broth anytime the pot looks dry or the onions start sticking too much
- Let the broth simmer uncovered for the last 10 minutes if it seems thin, to help it reduce slightly
- Grate your own Gruyere from a block for smoother, more even melting under the broiler
Serving Suggestions
This soup is hearty enough to serve as a light main course, especially alongside something green and simple. It also works well as a starter before a bigger meal.
- A crisp green salad with a light vinaigrette
- A slice of my Vegetarian Spinach and Feta Quiche for a full brunch spread
- Extra toasted baguette on the side for dipping
- A glass of the same dry white wine you cooked with
- Roasted vegetables for a heartier dinner plate
Variations of Vegetarian French Onion Soup
Once you have the base method down, this soup is easy to adjust to whatever you have on hand or however you like to eat.
My White Bean and Kale Soup is another good example of how a few swaps can completely change a soup’s personality.
- Swap in shallots for half the onions for a slightly sweeter, milder flavor
- Use cognac or brandy instead of sherry for a deeper, boozier finish
- Stir in a spoonful of miso paste along with the broth for extra umami depth
- Make it vegan by using olive oil instead of butter and a good melting vegan cheese
- Add a splash of balsamic vinegar near the end for a touch of tang
Storage and Reheating
This soup keeps well and honestly tastes even better the next day, once the flavors have had time to settle.
Just keep the bread and cheese separate until you are ready to serve again.
- Store the soup base in an airtight container in the refrigerator for up to 4 days
- Freeze the soup base, without bread or cheese, in a freezer safe container for up to 2 months
- Thaw frozen soup overnight in the refrigerator before reheating
- Reheat gently on the stovetop over medium low heat until warmed through
- Add fresh toasted bread and cheese, then broil again just before serving
Nutritional Facts
One serving of this soup, made with the ingredients listed above and topped with bread and cheese, comes in at roughly 340 calories.
My Roasted Carrot Ginger Soup is a lighter option if you are watching calories more closely.
Each bowl provides approximately 12 grams of protein, 34 grams of carbohydrates, and 17 grams of fat, along with a good amount of calcium from the cheese.
These numbers will vary depending on the exact broth and cheese you use.
Health Benefits of Key Ingredients
Beyond being comforting, this soup actually brings some real nutritional value to the table.
My Lentil Spinach Soup Recipe is another vegetarian option built around similarly nourishing ingredients.
- Onions are rich in antioxidants called flavonoids, which may support heart health
- Garlic contains compounds linked to immune support and healthy circulation
- Gruyere cheese provides calcium and protein to help make this a more balanced meal
- Fresh thyme adds vitamin C and has natural antibacterial properties
- Vegetable broth is naturally low in fat while still adding minerals to the dish
FAQs About Vegetarian French Onion Soup
1. Can I make this soup vegan?
Yes, simply swap the butter for olive oil and use a good melting vegan cheese in place of the Gruyere.
Double check that your Worcestershire sauce is vegan, since some brands contain anchovies.
2. Why do my onions taste bitter instead of sweet?
Bitter onions usually mean the heat was too high and they browned too quickly instead of slowly caramelizing.
Lower the heat and give them more time, stirring occasionally so they cook evenly without scorching.
3. Can I make this soup ahead of time?
Absolutely, the soup base can be made up to 4 days in advance and actually tastes better once the flavors have had time to meld.
Simply reheat the base and add fresh bread and cheese right before serving, similar to how you would prep my Vegetarian Egg Drop Soup Recipe in stages.
4. What can I use instead of sherry?
A dry white wine works well in its place, or you can leave out the alcohol entirely.
If you skip the wine, add a bit more broth along with a splash of apple cider vinegar to keep that same bright note.
5. My broiler is melting the cheese unevenly. What went wrong?
This usually happens when the bowls are not the same distance from the heat source or the cheese was piled unevenly.
Rotate the baking sheet halfway through broiling and keep a close eye on it, since cheese can go from perfectly melted to burnt in seconds.
Vegetarian French Onion Soup
Ingredients
- 4 tablespoons unsalted butter
- 1 tablespoon olive oil
- 3 pounds yellow onions about 6 large onions, thinly sliced
- 1 teaspoon salt plus more to taste
- 1/2 teaspoon sugar helps the onions caramelize
- 3 cloves garlic minced
- 2 tablespoons all purpose flour
- 1/2 cup dry sherry or dry white wine
- 6 cups vegetable broth
- 2 cups mushroom broth or extra vegetable broth
- 2 bay leaves
- 4 sprigs fresh thyme plus more for garnish
- 1 tablespoon vegetarian Worcestershire sauce
- 1/2 teaspoon black pepper
- 1 baguette sliced into 1/2 inch rounds
- 2 cups shredded Gruyere cheese
- 1/2 cup grated Parmesan cheese optional
Equipment
- Dutch oven or other heavy bottomed pot Enameled cast iron recommended for even heat distribution
- Mandoline slicer For evenly thin onion slices
- Broiler safe soup crocks or oven proof bowls Stoneware recommended
- Sharp chef’s knife
- Wooden spoon
- Ladle
- Baking sheet
Method
- Peel and thinly slice the onions, then mince the garlic.
- Melt butter with olive oil in a Dutch oven over medium heat. Add onions, salt, and sugar, then cook for 15 minutes until softened. Reduce heat to medium-low and cook for 35-45 minutes, stirring occasionally, until deep golden brown.
- Add garlic and cook for 1 minute. Stir in flour and cook for 2 minutes. Pour in sherry and deglaze the pot, simmering for 2-3 minutes. Add vegetable broth, mushroom broth, bay leaves, thyme, Worcestershire sauce, and pepper.
- Bring soup to a gentle boil, then reduce heat to low and simmer partially covered for 25-30 minutes. Season with salt and pepper to taste. Remove bay leaves and thyme sprigs.
- Preheat broiler and arrange baguette slices on a baking sheet. Broil for 1-2 minutes per side until lightly golden and crisp.
- Ladle hot soup into broiler safe bowls. Top each with 1-2 toasted baguette slices and sprinkle generously with Gruyere and Parmesan. Broil for 2-4 minutes until cheese is melted and bubbly. Let cool slightly before serving.
Nutrition
Notes
- Do not rush the caramelizing step – low and slow heat is what builds real flavor in the onions. This can take up to 45 minutes total.
- Use a wide, heavy bottomed pot so the onions have room to spread out and brown evenly.
- Deglaze with a splash of broth anytime the pot looks dry or the onions start sticking too much.
- Let the broth simmer uncovered for the last 10 minutes if it seems thin, to help it reduce slightly.
- Grate your own Gruyere from a block for smoother, more even melting under the broiler.
- Store the soup base in an airtight container in the refrigerator for up to 4 days. Keep bread and cheese separate until serving.
- Freeze the soup base, without bread or cheese, in a freezer safe container for up to 2 months.
- To make this soup vegan: swap butter for olive oil and use a good melting vegan cheese. Double check that your Worcestershire sauce is vegan.
- Swap in shallots for half the onions for a slightly sweeter, milder flavor. Use cognac or brandy instead of sherry for a deeper finish.
- Stir in a spoonful of miso paste along with the broth for extra umami depth, or add a splash of balsamic vinegar near the end for tang.
Private Notes
Tried this recipe?
Let us know how it was!Conclusion
This Vegetarian French Onion Soup is proof that a meatless version of a classic can still deliver all the cozy, savory comfort you are craving.
Give the onions the time they deserve and the rest of the recipe comes together easily.
I would love to hear how yours turns out, so leave a comment below and let me know what you served it with.
If you make this soup, feel free to share a photo here, and pass this recipe along to anyone who needs a good vegetarian dinner idea.
Recommended:
- Vegetarian Baked Spaghetti Recipe
- French Onion Beef Short Rib Soup Recipe
- Sweet Potato Soup Recipe
- Apple Butternut Squash Soup
- Broccoli Cheddar Soup Recipe
