Onion

Slow Cooker Onion Soup

Emma Sullivan By Emma Sullivan 4.7 (312 reviews)
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Slow Cooker Onion Soup

Slow cooker onion soup is the lazy cook's dream - all the deep, caramelized flavor of traditional French onion soup without standing at the stove for an hour. Just load up your slow cooker in the morning and come home to pure comfort.

The magic happens over 8-10 hours on low heat. The onions slowly release their sugars and transform into a mahogany-colored, deeply sweet base. It's truly set-it-and-forget-it cooking at its finest.

Slow Cooker Benefits

  • Hands-off: No stirring required
  • Even cooking: Gentle, consistent heat
  • Deep flavor: Long cooking = complex taste
  • Easy cleanup: One pot cooking

Tips for Success

  • Don't lift the lid - it releases heat
  • Use low setting for best caramelization
  • Add broth in last 30 minutes
  • Season at the end

Serving Suggestions

  • Crusty bread
  • Melted cheese on top
  • Fresh thyme
  • Weeknight dinner hero
Letting the soup simmer to develop rich flavors.
Letting the soup simmer to develop rich flavors.

Slow Cooker Onion Soup

A hands-off caramelized onion soup that cooks while you're away. Set it and forget it.

Prep: 20 min
Cook: 8 hr
Total: 8 hr 20 min
Servings:
8

Nutrition per serving

225 Calories
6g Protein
24g Carbs
11g Fat
3g Fiber

Ingredients

Instructions

  1. . Slice onions and add to slow cooker.
  2. . Add butter and cook 8-10 hours on low.
  3. . Add broth and seasonings.
  4. . Cook 30 more minutes. Serve.

Recipe Notes

  • Faster caramelization: Cook with lid cracked last 2 hours.
  • Gratinée style: Add bread and cheese, broil in oven-safe bowls.
  • Make-ahead: Keeps warming in slow cooker for 2 hours.
  • Storage: Refrigerate 5 days. Freezes excellently 3 months.