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4.80 from 5 votes

Vegetarian French Onion Soup (Slow Cooker)

Vegetarian French Onion Soup is the perfect comfort dinner and is great alone or paired with a salad.
Prep Time45 mins
Cook Time5 hrs
Total Time5 hrs 45 mins
Course: Dinner
Cuisine: American
Servings: 6 servings
Calories: 159kcal
Author: Stephanie



Instructions for caramelizing onions:

  • Melt 2 tbsp. butter with olive oil over medium heat in pan on stove top or instant pot if using.
  • Place onions in pan and cook 10 minutes, then sprinkle with salt.
  • Cook additional 20 minutes until caramelized and drizzle with balsamic vinegar last couple minutes of cooking.

Crockpot instructions:

  • Place caramelized onions in crockpot, along with remaining ingredients  reserving cheese and croutons for topping.
  • Cook on high 5 hours.
  • Remove bay leaf before spoon into bowls.
  • Spoon in oven safe serving bowls and top with croutons and cheese.
  • Melt until bubbly and golden brown.

Stovetop instructions:

  • Follow instructions above for caramelizing onions.
  • Add remaining ingredients and cook on low on stovetop 45-55 minutes.
  • Remove bay leaf prior to serving and adding cheesy croutons.

Instant Pot instructions using slow cooker function:

  • Set the instant pot on the sauté function and melt the 2 tbsp. of butter with olive oil.
  • Add thinly sliced onions and stir every few minutes for about 10 minutes before adding salt.
  • Continue to sauté onions stirring frequently as needed about 15-20 more minutes till they start to brown and caramelize.
  • Drizzle with balsamic vinegar the last minute of cooking.
  • Turn off Instant Pot, add remaining ingredients and stir.
  • Cover with lid. I recommend using a tempered glass lid that you can get for the instant pot. You can however use the lid that came with the instant pot and set to vent for slow cooking.
  • Set Instant Pot to slow cooker function. Adjust to high setting using the + button until you see the more button is on.
  • Then set timer for 6 hours and 30 minutes.
  • Remove bay leaf, serve immediately or add croutons and cheesy topping and melt under broiler.


Mix the tapioca flour or cornstarch with water prior to adding to soup.
Nutrition information is based off soup alone and doesn't include cheesy crouton topping.


Serving: 1serving | Calories: 159kcal | Carbohydrates: 12g | Protein: 4.9g | Fat: 10.6g | Saturated Fat: 5.3g | Sodium: 523mg | Potassium: 177mg | Fiber: 1.6g | Sugar: 5.2g | Calcium: 27mg | Iron: 1mg