Go Back
Bowl of Slow Cooker Onion Soup topped with melted cheese and fresh thyme on a wooden table

Slow Cooker Onion Soup

This Slow Cooker Onion Soup is a time-saving comfort food that combines rich, caramelized flavors with minimal effort. Enjoy a hearty, satisfying homemade onion soup recipe that delivers incredible taste with ease.
Print Recipe Pin Recipe
Prep Time 30 minutes
Cook Time 8 hours
Resting Time 30 minutes
Total Time 8 hours 30 minutes
Servings: 4 servings
Course: Main Course
Cuisine: American
Ingredients Equipment Method Notes

Ingredients
  

  • 30g/1oz butter diced
  • 800g/1lb 12oz onions thinly sliced
  • 1½ tsp roughly chopped thyme leaves (optional)
  • 1½ tsp sugar
  • 1.2 litres/2 pints beef or vegetable stock (made from 2 stock cubes)

Equipment

  • Slow Cooker
  • Sharp knife
  • Wooden spoon

Method
 

  1. Add the butter, onions, thyme (if using), and sugar to your slow cooker. Stir to coat the onions evenly.
  2. Set the slow cooker to high and cover. Cook for 6–8 hours, stirring occasionally, until the onions are deeply golden and caramelized.
  3. Pour in the stock, stir, and cook for an additional 30 minutes to let the flavors meld together.
  4. Ladle the soup into bowls and serve hot. Pair with crusty bread or a cheesy toast topping for the ultimate comfort meal.

Notes

Shortcut alert: Pre-sliced onions from the grocery store work great here if you’re short on time. Just make sure they’re fresh and not frozen, as frozen onions tend to release too much moisture during cooking.