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This deliciously cheesy Brussel sprout casserole is an excellent side dish to serve with your Thanksgiving or holiday dinner. Easy to make, this vegetarian gratin recipe is always a real crowd pleaser even if you’re not a fan of brussels!
Table of Contents
Why you’ll love this brussel sprout casserole
- Easy to make! While the halved Brussels sprouts roast, make a creamy sauce on the stove and then simply pour the sauce over the sprouts and bake!
- Perfect for the holidays. Add this easy side dish to your Thanksgiving spread for something cheesy!
- Great for any weeknight meal. This vegetarian brussel sprouts dish is a fun twist on a au gratin recipe substituting brussels sprouts for the potatoes. You can pair it with a main dish, like Pan Seared Chicken Thighs, Lemon Pepper Salmon, or a delicious Cast Iron Skillet Steak!
Ingredients to make Brussel Sprout Casserole
- Brussel sprouts: Start by peeling the outer yellowish layers. These are typically bitter. Then just trim the ends and slice in half.
- Oil: I like to use olive oil, but avocado would also work well to toss them in before roasting.
- Seasoning: Just a pinch of salt, pepper, and garlic powder.
For the sauce
- Butter: For sautéing the onions and cooking the roux.
- Onions: Chop your onions finely so it melts seamlessly into the sauce.
- Flour: Use about 2 tablespoons to make the roux. You want to cook the flour for about 2 minutes to cook out the flour taste.
- Mustard Powder: This adds a little bit of tangy and savory flavor.
- Milk: I like to use low fat milk, but regular or plant based milks would also work.
- Gruyere cheese: Gruyere cheese is a great melting cheese and really adds the final touch to your casserole.
How to make the recipe
- Cut brussel sprouts and place them in a baking dish and season. Give them a good toss
- Roast until golden brown; you can toss half way through if you’d like.
- Make the creamy sauce in a saucepan on the stovetop, and pour over the roasted Brussels sprouts.
- Sprinkle cheese on top of that creamy sauce and bake one more time until the cheese is bubbly.
Tips for making brussel sprout au gratin
- Remove the outer leaves of the sprouts before roasting them. The outer leaves can be dry and tough, so just peel them off before you cut the sprouts in half.
- Ensure that the sprouts are well covered with the oil. Use your hands to toss them so that the sprouts are fully covered and they will crisp up all over. I always use my hands for coating vegetables before roasting…it’s just the best way to coat them!
- Make this Brussel sprout casserole gluten-free. Use 1:1 GF flour when making the sauce instead of all-purpose. You can also use almond flour if you’d like.
- Opt for smaller sprouts when shopping. The smaller ones have more mild flavor so they don’t have that strong cruciferous taste that the bigger ones have. This is especially helpful for first-time brussel eaters!
Frequently asked questions
If you want to get ahead with things, you can either make the whole dish ahead of time and then reheat it in the oven to serve, or roast the spouts the day before and keep them covered in the fridge and then carry on with the recipe the next day. They may soften though so I prefer them roasted the same day.
Yes! This spout casserole freezes really well. Let the gratin cool completely before wrapping the dish in foil and placing it in a freezer bag. It will keep well for up to 2 months and can be thawed in the fridge overnight before reheating. You can also freeze individual portions in freezer safe containers or sealable bags.
More recipes with brussel sprouts:
- Parmesan Brussel Sprouts
- Brussel Sprout Sweet Potato Salad
- Air Fryer Brussel Sprouts
- Oven Roasted Brussel Sprouts
- Pan Roasted Brussel Sprouts
- Brussel Sprout Caesar Salad
If you’ve tried this healthy-ish feel good Brussel Sprout Casserole recipe or any other recipe on FeelGoodFoodie, then don’t forget to rate the recipe and leave me a comment below! I would love to hear about your experience making it. And if you snapped some shots of it, share it with me on Instagram so I can repost on my stories!
Brussel Sprout Casserole
- 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.
- 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.
Nutrition information provided is an estimate. It will vary based on cooking method and specific ingredients used.