This slow cooker french onion soup is slow-simmered to perfection, packed with sweet caramelised onions and rich broth, topped with cheesy toasts. A simple, hands-off twist on the classic French bistro dish!
I found the original recipe on the Spend with Pennies website...I was searching for recipes made in the slow cooker, and the ingredient list for this one sounded delicious. It's not a soup I'd eaten very often, but I was expecting a lovely full of flavour beefy broth and super tender sweet caramelised onions...and that's what you get from this recipe. Add to that oozy cheesy toast on top and it's the perfect combination.
Tips
- Sherry substitutes - brandy, dry vermouth, port, madeira or marsala are all good substitutes if you don't have dry sherry.
- This slow cooker french onion soup recipe is easily halved if you’re cooking for less people.
FREQUENTLY ASKED QUESTIONS
Set on low for 8 to 10 hours, or high for 4 to 5 hours. Stir occasionally, if possible, for even browning.
Yes - but the onions will have a slightly lighter, sweeter flavour. Sautéing first gives a deeper, richer flavour.
Yes - use vegetable stock and ensure the cheese is vegetarian-friendly.
Transfer leftover soup (without the bread topping) to an airtight container and keep in the fridge for up to 4 days. Reheat gently on the hob.
Yes - freeze without bread or cheese toppings. Thaw overnight in the fridge and reheat on the hob.
A sturdy baguette or sourdough slices work best — they soak up the soup without becoming too soggy.
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How to make this Slow Cooker French Onion Soup
Ingredients
- 1kg onions, finely sliced
- 45g butter
- 30g brown sugar (I use soft light brown)
- 1.8l beef stock (made with stock cubes or pots
- 1 tbsp Worcestershire sauce
- 1 clove garlic, crushed
- 75ml dry sherry (see Tips)
- 4 sprigs fresh thyme, or 1 tsp dried thyme
- 1 bay leaf
- slices of French baguette or bloomer bread (they need to be thickly sliced!)
- salt and freshly ground black pepper
- 150g gruyere or comte cheese, grated
Instructions
- In a large frying pan, cook the onions, butter and brown sugar over a medium to low heat for about 20 minutes until soft and caramelised.
- Once golden, add to them to the slow cooker along with the remaining ingredients except the bread and cheese.
- Cook on low for 6 to 8 hours (I find 6 hours is enough). Heat the grill to high about 5 minutes before the end of the soup cooking time.
- Grill one side of each slice of bread until lightly golden. Remove and discard the bay leaf and thyme sprigs from the soup, check the seasoning and add, to taste. Ladle the soup into bowls and place bread on the soup (you might need to cut the slices of bread in halves depending on what kind you use), toasted side onto the soup, then top with grated cheese. Place the bowls onto a baking tray and then grill for 2 to 3 minutes or until cheese is melted and browned. Enjoy...with some extra oozy cheesy toast on the side...if you fancy!
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Slow Cooker French Onion Soup
Ingredients
- 1 kg (2.2 lb) onions finely sliced
- 45 g (1.6 oz) butter
- 30 g (1.1 oz) brown sugar (I use soft light brown)
- 1.8 litre (7 ½ cups) beef stock (made with stock cubes or pots)
- 1 tbsp Worcestershire sauce
- 1 clove garlic crushed
- 75 ml (⅓ cups) dry sherry (see Notes)
- 4 sprigs fresh thyme, or 1 tsp dried thyme
- 1 bay leaf
- slices of French baguette or bloomer bread (they need to be thickly sliced!)
- salt and freshly ground black pepper
- 150 g (5.3 oz) gruyere or comte cheese grated
Instructions
- In a large frying pan, cook the onions, butter and brown sugar over a medium to low heat for about 20 minutes until soft and caramelised.
- Once golden, add to them to the slow cooker along with the remaining ingredients except the bread and cheese.
- Cook on low for 6 to 8 hours (I find 6 hours is enough). Heat the grill to high about 5 minutes before the end of the soup cooking time.
- Grill one side of each slice of bread until lightly golden. Remove and discard the bay leaf and thyme sprigs from the soup, check the seasoning and add, to taste. Ladle the soup into bowls and place bread on the soup (you might need to cut the slices of bread in halves depending on what kind you use), toasted side onto the soup, then top with grated cheese. Place the bowls onto a baking tray and then grill for 2 to 3 minutes or until cheese is melted and browned. Enjoy...with some extra oozy cheesy toast on the side...if you fancy!
Notes
- Sherry substitutes - brandy, dry vermouth, port, madeira or marsala are all good substitutes if you don't have dry sherry.
- This slow cooker french onion soup recipe is easily halved if you’re cooking for less people.
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Nutrition
Nutrition information is automatically calculated, so should only be used as an approximation.
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