Slow Cooker 5 Onion Soup

Course Soup
Servings 8


  • 4-6 lbs white, yellow, sweet, and red onions peeled and thinly sliced
  • 3 Tbsp olive or vegetable oil
  • salt and pepper to taste
  • 1 Tbsp granulated sugar optional
  • 2 tsp balsamic vinegar optional
  • 1/2 cup cooking sherry or other dry white wine
  • 7 cups beef broth low-sodium
  • 1 Tbsp Worcestershire sauce
  • 1 bay leaf
  • 1 clove garlic minced
  • 4 sprigs fresh thyme or 1 tsp dried
  • 1 Bay leaf
  • 8 slices dry french bread
  • 3/4 cup Gruyere cheese shredded
  • 1/2 cup chives for garnish


  • Transfer all of the thinly sliced onions to the slow cooker — the slow cooker should be half to three-quarters full. Cook for 5 hours on HIGH or 10 hours on LOW.
  • Stir occasionally, if possible — this will help them cook more evenly but is not necessary.
  • After 5-10 hours, the onions will be golden-brown and soft, and they will have released a lot of liquid. Remove onions to a large bowl and let cool.
  • If you like onions with a deeper color, continue cooking for another 3 to 5 hours on LOW. Leave the lid ajar so the liquid can evaporate. Check every hour and stop cooking whenever the onions look and taste good.
  • Stir sherry, Worcestershire sauce and beef broth into the remaining onions in the slow cooker bowl.
  • Add garlic, thyme, bay leaf and set on high for 4-6 hours OR low for 8-10 hours.
  • Discard bay leaf and ladle the soup into oven-safe bowls.
  • Top with dry bread slices and distribute Gruyere cheese evenly over each piece. Broil 2-3 minutes or until cheese is melted and browned.


Recipe provided for the National Onion Association by chef and blogger Nikki Miller-Ka.