This Brussel Sprout Casserole is a show-stopping side dish, made with fresh brussels sprouts and homemade cream of mushroom soup. It’s bursting with flavor, but also healthy, vegetarian and gluten free!

This recipe is made from scratch, but easy to prep in just 15 minutes. It’s perfect for everything from holiday meals to weeknight dinners!

cooked brussels sprouts in serving bowl with creamy mushroom sauce

It’s Thanksgiving Week on the blog, one of my favorite weeks of the year! Two weeks from tomorrow, Thanksgiving will be here and I want to make sure you’re prepared with some delicious new recipes for the big feast!

This brussels sprout casserole recipe was inspired by my desire to update the classic Green Bean Casserole. You know it, I know it. Canned green beans, canned cream of mushroom soup, topped with a bag of crispy fried onions.

While it is a classic dish, fresh and healthy, it is not. I know that a lot of people really love this creamy vegetable side dish, so I decided to give it an update!

Instead of canned green beans, I used fresh brussels sprouts and made my own cream of mushroom soup with fresh portobello mushrooms. I used cornstarch as a thickener instead of flour. This is one of my favorite gluten free cooking tips. Cornstarch is a wonderful thickening substitute for flour!

The result was an incredibly delicious, still creamy, rich and decadent, vegetarian & gluten free brussel sprout casserole. I’ve been making this recipe for holidays and beyond since 2014 and it always receives rave reviews!

While it is perfect for Thanksgiving or holiday meals, it’s also easy enough to pair with a Bacon Wrapped Meatloaf or Chicken Pot Pie for a delicious meal anytime of the year!

ingredients for brussel sprout casserole

Ingredients

  • Unsalted butter
  • Baby bella or portobello mushrooms – baby bella mushrooms are simply small portobello mushrooms. You can usually find both at the grocery store in the produce section and either one will work great in this recipe!
  • Salt
  • Black pepper
  • Fresh thyme
  • Garlic cloves
  • Ground nutmeg
  • Cornstarch
  • Vegetable broth – if you’re not vegetarian, you can substitute chicken or turkey broth.
  • Half-and-half – this is a combination of half milk and half heavy cream, easily found on the dairy aisle of most major grocery stores.
  • Fresh brussels sprouts
  • Parmesan cheese

All of the ingredient measurements can be found at the bottom of the post in the recipe card.

collage of images showing how to make brussels sprouts casserole

Step by step instructions

  1. Cook the mushrooms. Melt butter in a large skillet on the stove over medium-high heat. Add diced portobello mushrooms, salt, pepper, and thyme. Cook the mushrooms for 5-6 minutes.
  2. Season the mushrooms. Add minced garlic and nutmeg to the skillet, cook for another 2-3 minutes.
  3. Make a roux with the mushrooms. Sprinkle cornstarch over the mushrooms, then pour vegetable broth into the skillet. Stir all of the ingredients together and simmer for 1-2 minutes.
  4. Add half-and half to the skillet and stir to combine everything. Reduce the heat on the stove to medium-low and simmer for 6-8 minutes.
  5. Prep the brussels sprouts. Cut the ends off of the brussels sprouts and discard the outer leaves. Slice them into quarters, if they’re on the larger side, or in half, if they’re on the smaller side. Place them in a 9 inch x 12 inch oven-safe baking dish, or a casserole dish of similar size.
  6. Assemble the brussel sprout casserole. Pour the homemade cream of mushroom soup over the brussels sprouts in the baking dish and toss to coat the sprouts in the soup. Top with grated parmesan cheese. Place uncovered in a 350°F oven and bake for 40 minutes.
mushroom brussel sprout casserole in white baking dish with fresh thyme

Frequently asked questions

  • Do I need to boil or blanch the brussels sprouts for this casserole? No. The brussels sprouts will cook in the oven. There’s no need to boil or blanch them before adding them to the casserole dish.
  • How many people does this recipe serve? This casserole is the perfect size for a Thanksgiving dinner side dish for 4-6 people. If you’re cooking for a larger group, you’ll want to double the recipe. To do this hover over the “servings” amount in the recipe card below and adjust it from 4 to 8, to double the recipe. You can also adjust it up to 12 to triple the recipe. The ingredient amounts in the recipe card will automatically update to reflect the new serving amount.
  • How long will leftover brussel sprout casserole last in the fridge? Stored in an airtight container, this recipe will last in the fridge for up to 5 days.
  • How do you reheat the casserole? To reheat it, you can either place it in the oven or microwave. If using the oven, place the casserole back in an oven-safe dish, cover with foil and place it into an oven preheated to 350°F. Reheat for 10-15 minutes, or until the casserole is heated throughout. To reheat in the microwave, place the casserole on a microwave-safe plate and into the microwave for 2 minutes.
  • Can I use another type of cheese? Sure thing! Gruyere or sharp cheddar cheese would both be delicious on top of this casserole.
  • Can I make this recipe vegan? Yes! Use this Vegan Cream of Mushroom Soup recipe, pour it over the brussels sprouts in the baking dish and omit the parmesan cheese on top. Bake as instructed.

Make it into a meal

If you love this brussels sprout casserole recipe as much as I do, you might just want to throw in some protein and turn this side dish into a main dish. Here’s how to do it!

  • If you want to add chicken, slice one pound of boneless, skinless chicken breasts into cubes. Toss the chicken with 1 tablespoon olive oil, 1/2 teaspoon salt, 1/2 teaspoon black pepper and 1/2 teaspoon thyme. Heat a large skillet over medium-high heat. Add the chicken and cook for 5 minutes, flipping throughout the cooking time. Set the chicken aside. Prepare the homemade cream of mushroom soup. Add the brussels sprouts to the baking dish with the seared chicken pieces. Pour the mushroom soup over the sprouts and chicken, toss to coat, then sprinkle with the parmesan cheese and bake as instructed.
  • If you want to add bacon, omit the butter. Instead, add 4-6 slices of chopped thick-cut bacon to a large skillet over medium-high heat. Cook for 5-6 minutes, or until the bacon is crispy. Use a slotted spoon to remove the bacon from the skillet and place on a paper towel lined plate. Now use the bacon grease in the skillet to cook the mushrooms and prepare the mushroom soup. Continue the rest of the recipe as instructed. After the casserole has baked, stir the cooked bacon into the casserole before serving.
  • If you want to add sausage, place 3-4 sausage links on a baking sheet. During the last 20 minutes of cooking time on the casserole, add the baking sheet of sausages to the oven. Remove the casserole from the oven, along with the sausages. Slice the sausages, then toss them into the casserole before serving.
creamy baked brussel sprouts in white serving dish

What to serve it with

Perfect for Thanksgiving, but delicious year-round, pair this Brussel Sprout casserole with any of these tasty main dishes!

More brussels sprouts recipes

Fellow brussels sprouts lover? Then you’re guaranteed to be a fan of all of these recipes!

cooked brussel sprout casserole in white serving bowl
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Brussel Sprout Casserole with Mushrooms

This Brussel Sprout Casserole is a show-stopping side dish, made with fresh brussels sprouts and homemade cream of mushroom soup. It's bursting with flavor, but also healthy, vegetarian and gluten free!

Ingredients

  • 2 tablespoons butter
  • 6 ounces baby bella mushrooms, diced
  • 1 teaspoon kosher salt
  • 1 teaspoon black pepper
  • 1 teaspoon fresh thyme leaves
  • 2 cloves garlic, minced
  • ¼ teaspoon ground nutmeg
  • 2 tablespoons cornstarch
  • 1 cup vegetable broth
  • 1 cup half-and-half
  • 1 ½ pounds fresh brussels sprouts, trimmed and halved
  • ¼ cup grated parmesan cheese

Instructions

  • Preheat the oven to 350°F.
  • Add the butter to a large skillet on the stove over medium-high heat.
  • Once the butter is melted, add the diced mushrooms, salt, pepper, and thyme, cook for 5-6 minutes.
  • Add the minced garlic & nutmeg, cook for 2-3 minutes.
  • Sprinkle the cornstarch over the mushrooms, then pour the vegetable broth into the skillet and stir all of the ingredients together. Simmer for 1-2 minutes.
  • Reduce the heat to medium-low and add the half-and-half to the skillet.
  • Stir to combine everything, then simmer for 6-8 minutes.
  • In the meantime, add the halved brussels sprouts to a 9 inch x 12 inch oven-safe baking dish.
  • Cover with the creamy mushrooms and toss to coat the sprouts in the mushroom soup.
  • Top with the grated parmesan cheese.
  • Place in the oven and bake uncovered for 40 minutes.

Notes

  • If you’re not vegetarian, you can use chicken or turkey broth, instead of the vegetable broth.
  • To make this recipe vegan, use this Vegan Cream of Mushroom Soup recipe, pour it over the brussels sprouts in the baking dish and omit the parmesan cheese on top. Bake as instructed.
  • Gruyere or sharp cheddar cheese can be used in place of the parmesan cheese.
  • Leftover brussel sprout casserole, stored in an airtight container, will last in the fridge for up to 5 days.
  • To reheat the casserole, you can either place it in the oven or microwave. If using the oven, place the casserole back in an oven-safe dish, cover with foil and place it into an oven preheated to 350°F. Reheat for 10-15 minutes, or until the casserole is heated throughout. To reheat in the microwave, place the casserole on a microwave-safe plate and into the microwave for 2 minutes.
  • This casserole is the perfect size side dish for 4-6 people. If you’re cooking for a larger group, you’ll want to double the recipe. To do this hover over the “servings” amount above and adjust it from 4 to 8, to double the recipe. You can also adjust it up to 12 to triple the recipe. The ingredient amounts will automatically update to reflect the new serving amount.

Nutrition Facts

Serving 4gCalories 261kcal (13%)Carbohydrates 25g (8%)Protein 11g (22%)Fat 15g (23%)Saturated Fat 9g (45%)Cholesterol 43mg (14%)Sodium 1034mg (43%)Potassium 895mg (26%)Fiber 7g (28%)Sugar 5g (6%)Vitamin A 1855mg (37%)Vitamin C 145.9mg (177%)Calcium 207mg (21%)Iron 2.6mg (14%)
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