Easy Broccoli and Cauliflower Casserole
This make-ahead broccoli and cauliflower casserole has delicious creamy cheddar leek sauce and crunchy panko breadcrumb topping. It can be prepared a day ahead or you can make it and serve it right away.
I originally published this recipe on November 13th, 2015. I have updated some of the content to share it with you today. This post contains affiliate links.
Why We Love This Broccoli and Cauliflower Casserole
This casserole is a great addition to a holiday meal or can be served as a side dish for a Sunday supper. The savory yet light cream sauce pairs well with Pork Loin Roast, salmon baked in foil, baked crispy chicken and steak.
Because it can be made ahead, it is great for entertaining. Not only is it vegetarian, but it can be made gluten-free and lactose-free if desired so pretty much everyone can enjoy it.
Ingredients You’ll Need To Make This Casserole
- Cauliflower: You will need an entire head of cauliflower. Look for a medium sized head free from brown spots. Remove any leaves, and cut the core out before cutting into florets.
- Broccoli: You will need two large broccoli crowns (about 1 pound.)
- Olive Oil: To make this lower in saturated fat, we used olive oil instead of butter. The oil is used to saute the leeks, and it helps to make the breading on top brown and crisp nicely.
- Leek: The leek adds delicious flavor to the cheddar sauce. You only need the white and pale green parts, so you can chop off the green parts. Use them to make chicken stock. Follow instructions for how to clean a leek here.
- Salt: Note that we recommend table salt for this recipe. You may use kosher salt instead, but you will want to double it.
- Flour: To thicken the sauce, we used all-purpose flour. For gluten-free alternatives, we suggest using a cornstarch slurry instead of trying to use gluten-free flours. See more gluten-free tips below in our FAQs section.
- Milk: You can use regular milk or lactose-free milk. To keep this lower in calories, we used fat-free (skim) milk, but any type of milk will work.
- Cheddar: For the cheddar sauce, look for the sharpest available cheddar. That will give the sauce the strongest cheese flavor with only 1 1/2 cups.
- White Pepper: Creamy sauces are great with the flavor of white pepper. Black pepper can be substituted if unavailable.
- Panko: For crunchy golden topping, use panko breadcrumbs instead of regular fine breadcrumbs. IF you can find it, use whole-wheat for a tiny bit of additional fiber.
- Paprika and Garlic Powder: To season the breadcrumb mixture and give it color, use a combination of garlic powder and paprika.
Step-By-Step Directions To Make This Recipe
- STEP 1: Begin by bringing a large pot of salted water to a boil for blanching the vegetables. Set up a bowl of ice water.
- Step 2: Blanch cauliflower 3 minutes in boiling water. Remove from the water with a slotted spoon or small strainer and transfer immediately to the ice bath to stop it from cooking. Repeat with the broccoli, cooking for 3 minutes, and shocking in the ice bath. Drain the vegetables very well. Reserve bowl for mixing in step 7.
- Step 3: Prepare cheese sauce. Heat 2 tablespoons oil in a large saucepan over medium-high heat. Add leek and ¾ teaspoon salt and cook, stirring often until the leek is soft, 4 to 5 minutes.
- Step 4: Sprinkle the flour over the leek and stir to coat and the flour is evenly moistened.
- Step 5: Add milk and bring to a simmer, over high heat, stirring constantly. Cook until bubbling and thickened, 1 to 2 minutes longer.
- Step 6: Remove the sauce from the heat and stir in cheese and pepper until the cheese is completely melted into the sauce.
- Step 7: Preheat oven to 350 degrees F. Coat a 2 ½ quart baking dish with cooking spray. Mix the vegetables and cheese sauce together in the reserved bowl.
- Step 8: Transfer the veggie mixture to the prepared baking dish.
- Step 9: Stir panko, the remaining 1 teaspoon oil, paprika and garlic powder in a small dish until evenly moist. Top the broccoli and cauliflower mixture with the panko mixture.
- Step 10: Bake until the casserole is hot all the way through, the sauce is bubbling and the vegetables are tender, 28 to 35 minutes. Let cool 15 minutes before serving.
FAQs, Tips and Tricks For This Recipe
To make this gluten free, you’ll need to change up the sauce technique slightly. Here’s how:
Cook the leeks as directed.
Add 1 1/2 cups milk and heat until just steaming.
Whisk the remaining 1/2 cup milk with 2 tablespoons plus 1 teaspoon cornstarch in a small bowl.
Drizzle the cornstarch slurry into the steaming leek and milk mixture while whisking. Bring to a simmer while whisking.
Remove from the heat and stir in the cheese and pepper.
You will also have to purchase gluten-free panko. I like Ian’s brand.
To make this casserole lactose free, use a lactose free milk such as lactaid or Organic Valley Lactose Free milk and Cabot Cheddar (which is lactose free.)
You can use all cauliflower or all broccoli if you like. You could also substitute in halved Brussels sprouts for one or the other, but note that you will need to blanch it for 4 minutes 30 seconds.
This recipe can easily be prepped in advance and cooked just before you plan on serving it. To make this casserole ahead of time:
1. You’ll need to make the cheese sauce and blanch the veggies as directed in the recipe.
2. Then combine everything and transfer to your casserole dish.
Cover the casserole in foil and refrigerate up to 24 hours in advance. (note; do not add the breadcrumbs yet as they will pull too much moisture out of the casserole and will not crisp up again.)
3. Cook the casserole covered for 25 minutes.
4. Remove the cover, top with the breadcrumb mixture and bake until the casserole is hot all the way through, the sauce is bubbling and the vegetables are tender, 28 to 35 minutes.
More Broccoli and Cauliflower Side Dish Recipes
This Roasted Broccoli and Cauliflower with cheese is a simple side dish for weeknights or the holidays.
This lemon garlic broccoli is a popular recipe and one of my daughters all time favorite side dishes.
This simple steamed cauliflower with herbs is about as basic as it gets.
This Broccoli Mash with garlic is a great alternative and low carb side dish.
You will never guess that this keto-friendly cauliflower hummus is made with cauliflower instead of chickpeas!
Want more ideas for cauliflower? Don’t miss this Ultimate Guide to Cauliflower.
Other Delicious, Healthy Casserole Recipes To Try:
This is a great way to use up leftover turkey after Thanksgiving or for leftover chicken Chicken and Biscuits Casserole.
This is a great no canned soup comfort food meal that always gets great reviews: Chicken and Rice Casserole.
Here’s another cheesy holiday side which can be made ahead: Cheddar Green Bean Casserole.
This lower carb and veggie heavy Zucchini Casserole is a great way to use up a lot of zucchini.
Easy Fish Casserole: They say not to eat fish and cheese, but that’s because they’ve never tried this recipe inspired by my grandmother’s recipe.
Thanks so much for reading! If you are new here, you may want to sign up for my email newsletter to get a free weekly menu plan and the latest recipes right to your inbox. If you make this recipe, please come back and leave a star rating and review. I would love to hear what you thought!
Happy Cooking! ~KatiePrint
Broccoli and Cauliflower Casserole with Cheddar Leek Sauce Recipe
- Total Time: 1 hour 15 minutes
- Yield: 10 cups 1x
This make-ahead broccoli and cauliflower casserole is a healthy and delicious option for a covered dish for the holidays. The cauliflower and broccoli are coated in a creamy leek cheddar sauce and topped with crunchy panko breadcrumb topping.
- 1 medium head of cauliflower
- 2 large broccoli crowns (1 pound)
- 2 tablespoons plus 1 teaspoon extra-virgin olive oil, divided
- 1 large leek, white and pale green part only, sliced and washed
- ¾ teaspoon salt
- 1/3 cup all-purpose flour
- 2 cups fat-free milk (lactose-free if desired)
- 6 ounces sharp lactose free cheddar, shredded (I used Cabot Alpine)
- ¼ teaspoon ground white pepper
- ¼ cup panko, preferably whole-wheat
- 1 teaspoon paprika
- ¼ teaspoon garlic powder
- Core cauliflower and cut into medium florets. Cut off broccoli stems and cut into florets. Meanwhile, bring a large pot of salted water to a boil. Set a large bowl of ice water to the side.
- Blanch cauliflower 3 minutes in boiling water. Remove from the water with a slotted spoon or small strainer and transfer immediately to the ice bath to stop it from cooking. Repeat with the broccoli, cooking for 3 minutes, and shocking in the ice bath. Drain the vegetables very well. Reserve bowl for mixing in step 7.
- Prepare cheese sauce. Heat 2 tablespoons oil in a large saucepan over medium-high heat. Add leek and ¾ teaspoon salt and cook, stirring often until the leek is soft, 4 to 5 minutes.
- Sprinkle the flour over the leek and stir to coat and the flour is evenly moistened.
- Add milk and bring to a simmer, over high heat, stirring constantly. Cook until bubbling and thickened, 1 to 2 minutes longer.
- Remove the sauce from the heat and stir in cheese and pepper until the cheese is completely melted into the sauce.
- Preheat oven to 350 degrees F. Coat a 2 ½ quart baking dish with cooking spray. Mix the vegetables and cheese sauce together in the reserved bowl.
- Transfer the veggie mixture to the prepared baking dish.
- Stir panko, the remaining 1 teaspoon oil, paprika and garlic powder in a small dish until evenly moist. Top the broccoli and cauliflower mixture with the panko mixture.
- Bake until the casserole is hot all the way through, the sauce is bubbling and the vegetables are tender, 28 to 35 minutes. Let cool 15 minutes before serving.
TO MAKE AHEAD: Prepare through step 8 (do not pre-heat oven in step 7.) Cover casserole in foil and refrigerate up to 24 hours in advance. Preheat oven, and bake casserole covered for 25 minutes. Remove foil and continue with topping with the breadcrumb mixture and baking as directed in step 5.
- Prep Time: 30 minutes
- Cook Time: 30 minutes
- Category: Side Dish
- Method: Baked
- Cuisine: American
- Serving Size: 1 cup
- Calories: 171
- Sugar: 3 g
- Sodium: 377 mg
- Fat: 10 g
- Saturated Fat: 5 g
- Carbohydrates: 12 g
- Fiber: 2 g
- Protein: 8 g
Keywords: broccoli and cauliflower casserole, make ahead vegetable casserole, healthy broccoli casserole
The first time I made this it was great. The second time the vegetables were a little too crisp. So, the next time I made it, I blanched the vegetables for 5 min and did them all at once, also putting all into a colander and running cold water over. I made it a day before, putting in refrigerator overnight. I followed all the instructions but it came out very soggy, had to pour off liquid. Not sure what went wrong, but will go back to original instructions. The taste of this casserole is awesome and I won’t give up on it.
Thank you for reporting back and your star ratings! I appreciate that. I am not sure why it was undercooked the second time. My guess is that the florets were a little larger, perhaps? I’m glad you’re going to give it another try. Please let me know if you experience the problem again, as I would like to get to the bottom of that!
Hi. Can you use frozen broccoli and cauliflower. I have a lot to use up and am not sure how to cook it for this recipe. Thanks.
Yes I think that would actually be totally fine. Skip the blanching step all together. Thaw the veggies and make sure they are not dripping wet before continuing on with the next step.
Thank you! It worked fine with defrosted veggies. 🙂
This is such a good recipe! Even my kids loved it!! Thanks for sharing!
THank you so much! Amazing!
I love the lactose-free cheese sauce! Honestly, anytime I can add cheese sauce to my veggies it is a big win for both me and my kiddos! Thank you for sharing this super tasty recipe. We will definitely be making this again.
I’m glad to hear you tried the lactose free version. Yay!
Thank you for sharing looks absolutely delicious.
Thank you so much!
I am so happy I found this recipe. I didn’t even know there was dairy free cheese. I WAS WOWED by the fact that the cheese taste so much like real cheese. I made this 2020 while in quarantine since I started using instacart when I clicked the cheese link it took me to a near by place where they sell the cheese and I purchased it the same day and preped the veggies over night in the morning i just did the cheese. For lactose milk I used the oat milk it’s supposed to make it thicker as well and it came out super good my family loved it. I didn’t have leek in hand so I used the green onions and diced some white onion i added that to tye oil before putting in the milk. And the small one doesn’t even know there is diced green beans in there. Thank you so much for sharing this recipe. A video would be helpful. I will keep doing this and trying my own things now that I know there is lactose free cheese. Yay !!!
I’m so glad that you discovered it and liked it so much! Thanks so much Jessica.