Go Back
–+ servings
top down shot of baked casserole.

French Onion Soup Casserole

Author: Abbey McDermott
Everything you love about French onion soup baked together in a scrumptious casserole. A wonderful side dish for any seasonal meal.
4.63 from 8 votes
Print Recipe Save Recipe
Prep Time 10 minutes
Cook Time 1 hour 15 minutes
Total Time 1 hour 25 minutes
Course Side Dish
Cuisine American
Servings 6 - 8
Calories 459 kcal

Ingredients
  

  • 1 loaf sourdough bread (approx. 14 ounces)
  • 4 cups sliced yellow onions (such as Vidalia)
  • 3 tablespoons butter
  • 1 tablespoon fresh thyme (or 1 teaspoon dried)
  • salt and pepper
  • 1 teaspoon Worcestershire sauce
  • 1 teaspoon white wine vinegar
  • ¾ cup low-sodium beef broth (plus more as needed)
  • 8 ounces Gruyere cheese (shredded)

Instructions
 

  • Preheat the oven to 350℉.
  • In a large shallow oven-safe skillet over medium heat, melt the butter. Add the onions and toss to coat. Cook, stirring occasionally, until softened, 8-10 minutes.
  • Meanwhile, cut the bread into 1-inch cubes. Spread on a half-sheet pan and bake for 10-15 minutes until dry and slightly crisp. Set aside. Turn the oven up to 375℉.
  • When the onions are soft, add the thyme and season with salt and pepper. Continue cooking, stirring occasionally, until golden brown, 30-40 minutes. If the onions dry out, add 1-2 tablespoons of water as needed.
  • Stir in Worcestershire sauce and vinegar. Taste and season with salt and pepper as needed. Stir in bread and toss together.
  • Add the beef broth and stir to combine. The bread should be moist but not soupy. Add more broth if needed.
  • Add half of Gruyere cheese and fold together. Top with the remaining cheese.
  • Bake at 375℉ for 20-25 minutes until golden brown on top. Serve.

Notes

  1. Use freshly shredded cheese for the best flavor and melting quality.
  2. Don't rush the onions.  It takes time - and a little patience - to develop the sweet caramelization.
  3. To make ahead:  caramelize the onions up to 2-3 days in advance and store in the refrigerator.  Toast the bread cubes up to 2-3 days in advance and store them in an airtight container.  Combine the ingredients and bake according to the directions.
  4. Make extra caramelized onions to use in caramelized onion dip or on pizza like this fig, blue cheese, and caramelized onion flatbread.

Nutrition

Calories: 459kcal | Carbohydrates: 50g | Protein: 21g | Fat: 20g | Saturated Fat: 11g | Polyunsaturated Fat: 2g | Monounsaturated Fat: 6g | Trans Fat: 0.2g | Cholesterol: 57mg | Sodium: 898mg | Potassium: 308mg | Fiber: 4g | Sugar: 8g | Vitamin A: 592IU | Vitamin C: 10mg | Calcium: 455mg | Iron: 4mg

Nutritional information is an estimate and will vary depending on the exact amounts and specific ingredients used.

Tried this recipe?Please leave a comment and rating below.
Love this recipe? Follow on Pinterest for more inspiration!