Savory Vegetarian French Onion Soup

Here’s my cozy take on French onion soup, made completely vegetarian with a rich broth, slow-cooked caramelized onions, crusty bread, and plenty of melted cheese on top.

This meat-free version has become a regular at our dinner table during the cold months. I usually make a big batch on Sunday afternoons – the smell of onions cooking slowly fills the whole house with such wonderful aromas. And let’s be honest, who can resist that gooey cheese pull when you dig in?

What Kind of Onions Should I Use?

Yellow onions are the classic choice for French onion soup, and for good reason. They have the perfect balance of natural sugars that caramelize beautifully when cooked low and slow, creating that rich, sweet flavor that makes this soup so special. While white onions can work in a pinch, they’re generally a bit too sharp and don’t caramelize quite as nicely. Sweet onions like Vidalias can be used too, but keep in mind they might make your soup a touch sweeter than the traditional version. Just make sure your onions are firm and heavy for their size when you buy them, and avoid any that show signs of sprouting or soft spots.

Options for Substitutions

This cozy soup recipe is pretty adaptable – here’s what you can swap if needed:

• Yellow onions: Yellow onions are really the star here and can’t be substituted – they give that classic sweet, caramelized flavor that makes French onion soup what it is.
• Gruyere cheese: While Gruyere is traditional, you can use Swiss cheese, Emmental, or even a mix of mozzarella and parmesan. For vegan options, try vegan Swiss-style cheese or a cashew-based cheese that melts well.
• Red wine: No wine? Add an extra 1/2 cup of vegetable stock plus 1 tablespoon of balsamic vinegar to get that deep flavor.
• Worcestershire sauce: For a vegetarian version, use soy sauce or tamari mixed with a tiny splash of vinegar. You can also try miso paste (about 2 teaspoons) for that umami kick.
• French bread: Any sturdy bread works here – sourdough, country bread, or even a good quality gluten-free bread if needed. Just make sure it’s thick-cut and day-old for the best results.
• Fresh thyme: If using dried thyme instead of fresh, use 1 teaspoon since dried herbs are more concentrated. You could also use a mix of dried herbs like herbes de Provence.

Watch Out for These Mistakes While Cooking

The biggest mistake when making French onion soup is rushing the onion caramelization process – properly caramelized onions take at least 45-60 minutes of slow cooking to develop their rich, sweet flavor, so resist the urge to crank up the heat.

Another common error is overcrowding the pan with onions, which leads to steaming instead of caramelizing – use your largest pot and make sure the onions have enough space to cook evenly, stirring occasionally but not constantly.

The color of your onions is a crucial indicator – they should reach a deep golden brown (not pale yellow or burnt black), and if you notice brown bits sticking to the bottom of the pot, deglaze with a splash of stock or wine to incorporate those flavorful pieces back into the soup.

For the perfect finishing touch, don’t place your bread and cheese too far under the broiler, as they can go from perfectly melted to burnt in seconds – keep a close eye on them and position the rack in the middle of the oven rather than at the very top.

What to Serve With French Onion Soup?

French onion soup is pretty filling on its own, but I love to round out the meal with a few simple sides. A crisp green salad with a light vinaigrette helps balance out the rich, savory flavors of the soup – I usually toss together some mixed greens, sliced pears, and walnuts. For a heartier meal, serve the soup as a starter portion and follow it with a simple pasta dish or roasted vegetables. If you’re keeping things casual, some extra crusty bread on the side (besides what’s already floating on top of your soup!) never hurts for soaking up every last drop of that tasty broth.

Storage Instructions

Keep: This cozy vegetarian French onion soup tastes even better the next day! Place it in an airtight container in the fridge without the bread and cheese topping, and it’ll stay good for up to 5 days. The flavors actually develop more as it sits, making those onions even more flavorful.

Freeze: Want to save some for later? Let the soup cool completely, then pour it into freezer-safe containers or bags. It’ll keep well in the freezer for up to 3 months. Just remember to freeze only the soup base – add fresh bread and cheese when you’re ready to serve.

Reheat: To enjoy your soup again, warm it up slowly on the stovetop over medium-low heat, stirring occasionally. Once it’s hot, ladle it into oven-safe bowls, add fresh bread and cheese on top, and broil until the cheese gets all melty and golden. The soup should be just as good as day one!

Preparation Time	10-15 minutes
Cooking Time	90-100 minutes
Total Time	100-115 minutes
Level of Difficulty	Medium

Estimated Nutrition

Estimated nutrition for the whole recipe (without optional ingredients):

• Calories: 2000-2200
• Protein: 60-70 g
• Fat: 120-130 g
• Carbohydrates: 180-200 g

Ingredients

• 3 pounds yellow onions (approximately 5 large, peeled and sliced into thin half-moon shapes)
• 4 tablespoons olive oil
• 2 tablespoons butter (substitute with a vegan option if needed)
• 1 teaspoon sugar (coconut sugar is optional if preferred)
• 1 1/2 teaspoons salt
• 4 cloves garlic, finely minced
• 8 cups vegetable stock*
• 1/2 cup red wine**
• 1 tablespoon worcestershire sauce***
• 2 bay leaves
• 1 tablespoon fresh thyme (dried can be used, if preferred)
• 1/2 teaspoon ground black pepper
• 4 thick slices of french bread or similar loaf
• 1 cup grated gruyere cheese (either fresh or use vegan alternative)

Step 1: Caramelize the Onions

In a large pot, heat the olive oil over medium-high heat.

Once hot, add in the sliced onions.

Cook, stirring often, until the onions start to soften, about 20 minutes.

Add in the butter and continue to cook the onions until they begin to brown, approximately 15-20 more minutes.

Monitor closely and adjust the heat if necessary to prevent burning.

The onions should brown slowly for a rich, caramelized flavor.

Step 2: Add Seasonings and Deglaze

Stir in the sugar and salt, and continue cooking for another 15 minutes until the onions are well browned.

During the last couple of minutes, add the garlic and continue to stir.

Deglaze the pot by stirring in the red wine, using a wooden spoon to scrape any flavorful bits from the sides and bottom of the pot.

Step 3: Simmer the Soup

Add the vegetable broth, Worcestershire sauce, bay leaves, thyme, and black pepper to the pot.

Bring the mixture to a simmer, cover, and let it cook for 30 minutes.

Stir every few minutes to ensure all ingredients are well combined and to prevent sticking.

Step 4: Toast the Bread

Preheat the oven to 400 degrees F.

Brush or spray the slices of bread with oil or cooking spray, and place them on a baking sheet.

Toast for 10 minutes, flipping halfway through, until lightly toasted.

Once done, set aside for serving.

Step 5: Assemble and Broil the Soup

Season the soup to taste with additional salt and pepper if needed.

Ladle the soup into oven-proof bowls, top each with a slice of the toasted bread, and evenly sprinkle cheese across the bowls.

Place the bowls on a large baking tray and broil in the oven until the cheese is melted and bubbling around the edges.

Step 6: Serve and Enjoy

Carefully remove the baking tray from the oven and serve the soup immediately.

Enjoy the warm, comforting flavors of your homemade French onion soup!