French Onion Soup - Easy Slow Cooker Recipe - The Magical Slow Cooker (2024)

The Magical Slow Cooker » Recipes » Soups » Slow Cooker French Onion Soup

by Sarah Olson on | Updated 20 Comments

Jump to Recipe Jump to Video Print Recipe

Make Slow Cooker French Onion Soup in your slow cooker. It has a rich buttery onion broth that is great with homemade croutons and cheese broiled on top.

It’s soup season (actually, every season is soup season for me). My family also enjoys slow cooker baked potato soup and slow cooker ham and bean soup. If you want a chicken version of this soup, try my Slow Cooker French Onion Chicken recipe.

French Onion Soup - Easy Slow Cooker Recipe - The Magical Slow Cooker (1)

Crockpot French Onion Soup is just as good as any fancy restaurant. My version doesn’t just taste like beef broth and onions. I add butter, balsamic vinegar, and spices, so the soup has a depth of flavor and see my tips for making the croutons that go under the cheese when serving.

If you love this soup, then try my Slow Cooker French Onion Dip, or my Slow Cooker French Onion Pot Roast.

Recipe Ingredients

French Onion Soup - Easy Slow Cooker Recipe - The Magical Slow Cooker (2)
  • Onions – Use sweet yellow onions (white or yellow, or red onions work too)
  • Sugar – Optional, only use if you can’t find sweet yellow onions
  • Salted Butter – Used to caramelize the onions
  • Flour – Added to the butter and onions. This will add some body to the soup.
  • Beef broth – Can use chicken if desired.
  • Balsamic Vinegar – Adds flavor and touch of tang.
  • Worcestershire sauce – My secret ingredient.
  • Seasonings – Salt, pepper, oregano, thyme, garlic, and a bay leaf.
  • Toppings – Homemade Croutons (recipe below), swiss cheese, and parmesan cheese.

How to carmelize the onions:

  • Set a pan to medium-high heat. Add the butter. When the butter is melted, add the onions and sprinkle with salt and pepper.
  • Cook the sliced onions until browned and caramelized; this can take 10 or more minutes. Stir often.
  • I add the flour to the butter and onions and cook for 2 more minutes.
French Onion Soup - Easy Slow Cooker Recipe - The Magical Slow Cooker (3)
  • Add remaining ingredients.
  • Stir.

How long do I cook?

  • Place the lid on the slow cooker.
  • Cook on HIGH for 4 hours or on low for 8 hours.
French Onion Soup - Easy Slow Cooker Recipe - The Magical Slow Cooker (4)

How to make homemade croutons:

  • Preheat the oven to 500 degrees (broil).
  • Cut a baguette into 1/4 inch slices. Place slices on a sheet pan.
  • Using a pastry brush, brush olive oil onto the slices.
  • Place the sheet pan under the broiler. Cook for about 3-5 minutes or until browned and toasty.
  • Cut a garlic clove tip off and rub each piece of cooked bread with it. This will give the bread garlic flavor.

What Can I Use If I Don’t Have Bread?

  • Store-bought croutons – Yes! This works well. When I worked at Marie Callender’s, they used bagged croutons for their French Onion Soup.
  • Garlic bread or French Bread – Cut a loaf of store-bought garlic bread or French bread into cubes. Broil until crisp and browned.
  • Stove-top stuffing – This buttery onion soup is amazing topped with a bit of stuffing mix under the cheese.
French Onion Soup - Easy Slow Cooker Recipe - The Magical Slow Cooker (5)

How to serve this recipe:

  1. Fill an oven safe bowl with the French Onion Soup broth. Place the bowl in a pie tin or on a baking sheet. (You can make more than one bowl at a time).
  2. Add the homemade croutons (or store-bought) on top of the soup.
  3. Place 1-2 swiss cheese pieces (can use provolone or gruyere) and sprinkle on parmesan cheese.
  4. Broil until the cheese is golden brown and is bubbly.
French Onion Soup - Easy Slow Cooker Recipe - The Magical Slow Cooker (6)

What is the best cheese for this recipe?

  • Swiss Cheese or Baby Swiss
  • Gruyere Cheese
  • Mozzarella Cheese
  • Parmesan cheese – in addition to the above cheeses.

Can I freeze this soup?

  • Yes, you can freeze the leftover soup (without the croutons and cheese).
  • Place the cooled soup into freezer ziplock bags or freezer containtes.
  • Freezer for up to 3 months.
  • Thaw in fridge for 24 hours before needing.
  • Reheat on the stove-top or microwave.
French Onion Soup - Easy Slow Cooker Recipe - The Magical Slow Cooker (7)

Want to make more magic in your crockpot? Stay up to date and subscribe to my newsletter and follow along on Facebook, Instagram, Pinterest and YouTube.

French Onion Soup - Easy Slow Cooker Recipe - The Magical Slow Cooker (8)

Slow Cooker French Onion Soup Recipe

4.93 from 55 votes

Rich and decadent French Onion Soup made in a slow cooker. Top with homemade croutons and cheese, then broil.

Print Pin Rate

Course: Soup

Cuisine: American

Prep Time: 25 minutes minutes

Cook Time: 4 hours hours

Total Time: 4 hours hours 20 minutes minutes

Servings: 10

Calories: 132kcal

Author: Sarah Olson

Ingredients:

  • 1 stick butter
  • 5 sweet yellow onions sliced (white, yellow or red onions work too)
  • 1 tsp. salt
  • 1/4 tsp. pepper
  • 1/4 cup flour
  • 64 oz. beef broth or beef stock (two 32-oz. containers)
  • 1 tsp. sugar (optional) I only use this if my onions aren't labeled "sweet onions"
  • 2 tsp. minced garlic
  • 1/4 tsp. dried thyme (not ground)
  • 1/4 tsp. dried oregano (not ground)
  • 1 tsp. Worcestershire sauce
  • 1 Tbsp. balsamic vinegar
  • 1 bay leaf

For serving (not included in nutritional count)

  • 1 baguette
  • olive oil
  • 1 whole garlic clove
  • sliced swiss cheese (can use provolone or gruyere) (about 2 slices needed per serving)
  • shredded parmesan cheese (use about 1 tablespoon per serving)

Instructions:

  • In a large skillet set to medium high heat, add the butter. When the butter is melted add the sliced onions. Sprinkle with the salt and pepper.

  • Saute the onion until browned and caramelized. This will take about 10 minutes. Stir often. Adjust the heat if they start to burn.

  • When the onions are done cooking add the flour to the butter and onions. Cook for 2 more minutes.

  • Add the floured onions to the slow cooker. Add the beef broth, sugar (if using), garlic, thyme, oregano, Worcestershire sauce, and balsamic vinegar. Stir well. Add the bay leaf on top.

  • Cook on HIGH for 4 hours or LOW for 8 hours.

  • Remove bay leaf before serving.

How to make the homemade croutons:

  • Preheat the oven to 500 degrees (broil).

  • Cut a baguette into 1/4 inch slices. Place slices on a sheet pan.

  • Using a pastry brush, brush olive oil onto the slices.

  • Place the sheet pan under the broiler. Cook for about 3-5 minutes or until browned and toasty.

  • Cut a garlic clove tip off and rub each piece of cooked bread with it. This will give the bread garlic flavor.

How to assemble the bowls of soup:

  • Fill an ovenproof bowl with the French Onion Soup broth. Place the bowl in a pie tin or on a sheet pan. (You can make more than one bowl at a time).

  • Add the homemade croutons (or store-bought) on top of the soup.

  • Place 1-2 pieces of swiss cheese (can use provolone or gruyere) and sprinkle on parmesan cheese.

  • Broil until the cheese starts to brown and is bubbly.

How to Video:

Sarah’s Notes:

What can I use instead of bread for topping this soup?

  • Store-bought croutons – Yes! This works well. When I worked at Marie Callender’s, they used bagged croutons for their French Onion Soup.
  • Garlic bread – Cut a loaf of store-bought garlic bread into cubes. Broil until crisp and browned.
  • Stove-top stuffing – This buttery onion soup is amazing topped with a bit of stuffing mix under the cheese.

Can I freeze the leftover soup?

  • Yes, you can freeze the leftover soup (without the croutons and cheese).
  • Place the cooled soup into freezer ziplock bags or freezer containers.
  • Freezer for up to 3 months.
  • Thaw in fridge for 24 hours before needing.
  • Reheat on the stove-top or microwave.

Best cheeses for this recipe:

  • Swiss Cheese or Baby Swiss
  • Gruyere Cheese
  • Mozzarella Cheese
  • Parmesan cheese – in addition to the above cheeses.

Nutritional values do not include croutons or cheese (every bowl size will need different amounts of cheese and croutons, that is why I can not add this value).

Nutrition Information:

Calories: 132kcal | Carbohydrates: 9g | Protein: 3g | Fat: 10g | Saturated Fat: 6g | Cholesterol: 24mg | Sodium: 954mg | Potassium: 186mg | Fiber: 1g | Sugar: 3g | Vitamin A: 282IU | Vitamin C: 4mg | Calcium: 28mg | Iron: 1mg

Nutrition info is auto-generated. This information is an estimate; if you are on a special diet, please use your own calculations.

Made this recipe?I want to see your photos! Tag me on Instagram @themagicalslowcooker

Try one of these soups next:

  • Slow Cooker Stuffed Pepper Soup
  • Slow Cooker Broccoli Cheese Soup
  • Slow Cooker Corned Beef and Cabbage Soup
  • Slow Cooker Turkey Chowder
  • Slow Cooker Tomato Soup
  • Slow Cooker Black Bean Soup
  • Slow Cooker Chicken Noodle Soup

FREE EMAIL SERIESSLOW COOKER SECRETS

Get Sarah's tricks to delicious and hands-free cooking!
French Onion Soup - Easy Slow Cooker Recipe - The Magical Slow Cooker (2024)

FAQs

Is 4 hours on high the same as 8 hours on low in a slow cooker? ›

The difference between "High" and "Low" on slow cookers seems to differ with every brand and model. One thing that is consistent, though, is that food takes seven to eight hours to reach a simmer point (around 210°) on low; versus three to four hours on high.

Should you cook onions before putting in slow cooker? ›

It can be nice to cook the onions beforehand, as the flavour is different to when you put them in raw, but experiment both ways as you may find you prefer one. It can also be good to brown meat to give it some colour, but again, this is not essential.

What cannot be cooked in a slow cooker? ›

10 Foods You Should Never Make in a Slow Cooker
  1. Raw Meat.
  2. Seafood.
  3. Pasta.
  4. Rice.
  5. Delicate Vegetables.
  6. Boneless Skinless Chicken Breasts.
  7. Dairy.
  8. Wine and Other Liquor.
Jan 19, 2024

Do you put hot or cold water in a slow cooker when cooking? ›

Preheat the cooker and add hot liquids, if possible. Preheating the crock before adding ingredients or cooking on the highest setting for the first hour will ensure a rapid heat start and will shorten the time foods are in the temperature danger zone.

What happens if you slow cook on high instead of low? ›

Let's say you want to slow cook a pork roast recipe that calls for 8 hours on Low, but you need it done in much less than 8 hours. Switching to High for the sake of time savings can leave you with a roast that's dried out or even burned on the exterior, but undercooked and not at a food-safe temperature in the center.

Is 6 hours on low the same as 4 hours on high? ›

One hour on HIGH generally equals two hours on LOW.

Can you put raw onions in the slow cooker? ›

Just throw onions and butter in the slow cooker and let them cook for hours and hours and hours, without having to babysit the crock pot and stir them every few minutes, and go through the process of deglazing the pan?!?

Can you overcook onions in slow cooker? ›

How Long It Takes to Caramelize Onions in a Slow Cooker. It's almost impossible to overcook these onions, but I've found that 10 hours makes soft, lightly browned onions that still have a bit of bite.

Can you put uncooked onions in slow cooker? ›

Instructions: Add the alliums, enough oil to coat them and salt to your slow cooker. Stir well to coat and cook on low for 8 to 10 hours. If you like, add a tablespoon of molasses or brown sugar during the last hour or so.

What's the difference between slow cooker and crockpot? ›

However, Crockpots generally have ceramic or porcelain pots, while most slow cookers have a metal pot. As with a lot of cooking appliances, the biggest difference comes from the distribution of heat.

Why are my carrots still hard in the slow cooker? ›

If you don't have enough liquid in the pot, the carrots won't cook evenly and may stay tough. Aim for at least a cup or two of liquid, enough to reach about a third of the way up on the ingredients.

Which is better a crockpot or a slow cooker? ›

When it comes to cooking, you can use either. While Crock-Pot is just a brand name, Crock-Pots, Crock-Pot-style slow cookers, and other types of slow cookers will all get the job done.

What vegetables should not be added to a slow cooker? ›

Tender vegetables

Vegetables such as peas, asparagus and peppers can become a flavorless, mushy mess in a slow cooker. Stick to heartier root vegetables like potatoes, onions, leeks and yams, or wait to add the tender vegetables until the last 30 minutes or so of cooking time.

Is it safe to leave a slow cooker on overnight? ›

Yes, it's safe to leave a slow cooker on when you leave the house. The purpose of a slow cooker is to allow you to cook while you aren't home. Slow cookers simmer food slowly, killing bacteria and raising meat to the perfect internal temperature.

What is the best meat to cook in a slow cooker? ›

Choose the right cut: Chuck roasts, short ribs, pork shoulders and lamb shanks (think fatty and tougher meats) become meltingly tender with the moist, low heat of a slow cooker. Leaner cuts like pork tenderloin tend to dry out. Likewise, dark meat chicken — thighs, drumsticks, etc.

How do I convert slow cooker time from high to low? ›

If a recipe calls for cooking on the HIGH setting for three hours, you can cook it for seven hours on the LOW setting instead. Or if a recipe calls for eight hours on HIGH, it can be cooked for up to 12 hours on LOW.

Is 2 hours on high the same as 4 on low? ›

Converting temperatures and cook time

How long you cook a dish in your slow cooker depends on whether you set it on high or low and the recipe's original cook time. The general rule is the high setting cooks about twice as fast as the low setting.

What is the equivalent of 8 hours on low in slow cooker? ›

Cooking Conversions for Slow Cookers
Traditional Oven or Stovetop LowLow Slow Cooker Setting (about 200°F)High Slow Cooker Setting (about 300°F)
15-30 minutes4-6 hours1-1/2 to 2-1/2 hours
35-45 minutes6-8 hours3-4 hours
50 minutes- 3 hours8-10 hours4-6 hours
Dec 8, 2016

What is the equivalent of 8 hours on low in slow cooker to oven? ›

Oven cooking is often faster than slow cooking. As a general rule, a dish that takes 6–8 hours on a slow cooker's low setting might only need 2–3 hours in the oven at 325°F. Always check for doneness earlier than the original recipe suggests, especially if you're converting for the first time.

Top Articles
Latest Posts
Article information

Author: Rueben Jacobs

Last Updated:

Views: 6575

Rating: 4.7 / 5 (57 voted)

Reviews: 80% of readers found this page helpful

Author information

Name: Rueben Jacobs

Birthday: 1999-03-14

Address: 951 Caterina Walk, Schambergerside, CA 67667-0896

Phone: +6881806848632

Job: Internal Education Planner

Hobby: Candle making, Cabaret, Poi, Gambling, Rock climbing, Wood carving, Computer programming

Introduction: My name is Rueben Jacobs, I am a cooperative, beautiful, kind, comfortable, glamorous, open, magnificent person who loves writing and wants to share my knowledge and understanding with you.