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Brussel Sprout Casserole after baking in the oven with cheesy top
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5 from 139 votes

Brussel Sprout Casserole

Easy to make, this creamy and cheesy Brussel sprout casserole is a crowd pleasing side dish. Serve up the vegetarian gratin for Thanksgiving!
Course Side Dish
Cuisine American
Prep Time 15 minutes
Cook Time 35 minutes
Total Time 50 minutes
Servings 6 servings
Calories 143kcal
Author Yumna Jawad


  • 1 pound brussel sprouts trimmed and cut in half
  • 1 tablespoon olive oil
  • ½ teaspoon salt
  • ¼ teaspoon black pepper
  • ¼ teaspoon garlic powder
  • 1 tablespoon butter
  • ¼ cup finely chopped onions
  • 2 tablespoons all-purpose flour
  • 1 teaspoon mustard powder
  • 1 cup fat free milk
  • ½ cup grated Gruyere cheese divided


  • Preheat the oven to 425°F.
  • Place brussel sprouts on an 8 x 11 rimmed baking dish, drizzle with olive oil and season with salt, pepper and garlic powder. Toss to coat evenly, and then roast until golden brown, about 20-25 minutes, tossing halfway through.
  • In a small saucepan over medium heat, melt the butter. Add the onions and cook until translucent, about 3-5 minutes. Add the flour and mustard powder and stir until the flour dissolves, about 1-2 minutes. Slowly pour the milk and stir with a wooden spoon until the sauce thickens. Add ¼ cup gruyere cheese and stir until well blended.
  • When the brussel sprouts are done roasting, pour the sauce over the brussel sprouts. Sprinkle remaining gruyere cheese on top.
  • Return the brussel sprouts to the oven and cook until the cheese is melted and bubbly, about 15 more minutes. Serve warm.



Storage: Store any leftovers in an airtight container. They will last up to 3 days in the fridge.
Substitutes: For best results, follow the recipe as is. However here are some common substitutes that would work well in this recipe.
  • Instead of regular milk, you can use any unsweetened plant-based milk.
  • Instead of gruyere cheese, you can use shredded cheddar cheese or another one you like.
  • To make this gluten-free, use an all-purpose gluten-free flour mix. You can also substitute with almond flour.


Calories: 143kcal | Carbohydrates: 12g | Protein: 8g | Fat: 8g | Saturated Fat: 4g | Cholesterol: 18mg | Sodium: 284mg | Potassium: 376mg | Fiber: 3g | Sugar: 4g | Vitamin A: 816IU | Vitamin C: 65mg | Calcium: 193mg | Iron: 1mg