Cheesy Vegetarian Casserole (with Cauliflower Rice)

Cheesy Vegetarian Casserole (with Cauliflower Rice) is a tasty low-carb meatless dinner for people who like broccoli, mushrooms, and cheese. And this tasty casserole that’s loaded with vegetables has only 12.5 net carbs in a generous serving.

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Let me tell you the history behind this Cheesy Vegetarian Casserole (with Cauliflower Rice)! Years ago, I started my healthy eating journey with the original South Beach Diet. In those days I ate a lot more brown rice, whole grain pasta, and higher carb veggies than I do now. But now, although I still have readers who are South Beach Diet fans, I think most people who follow me now want recipes that are lower in carbs.

However, I still have some amazing recipes from those SBD days on the site, so I’ve been having fun adapting them into more carb-conscious versions. Years ago I created a Cheesy Vegetarian Brown Rice Casserole. (You can use that link to see the original recipe.) That casserole is still delicious, but high in carbs compared to the recipes I’m featuring now. 

So we decided that casserole needed an update, and Kara and I worked on it a few times to create this new low-carb vegetarian casserole that’s just as delicious. And this recipe is a bit more substantial than the original recipe, and also a bit more cheesy!

If you like broccoli, cauliflower, mushrooms, sour cream, and cheese, I bet you’re going to love this tasty casserole for a meatless main dish or a perfect side dish. I hope you’ll try the recipe!

What ingredients do you need for this recipe?

(This is only a list of ingredients; please scroll down for complete printable recipe. Or if you use the JUMP TO RECIPE link at the top of the page, it will take you directly to the complete recipe.)

• frozen cauliflower rice
• canned vegetable broth (affiliate link)
• mushroom base (affiliate link) or mushroom stock cubes (affiliate link), optional, but recommended
• sliced mushrooms
• onion
• broccoli
• olive oil
• Italian Herb Seasoning (affiliate link)
• Spike Seasoning (affiliate link), optional but recommended
• salt and fresh ground black pepper to taste
• sour cream
• grated sharp cheddar cheese
• Monterey Jack cheese

What frozen cauliflower rice did I use?

I used this frozen cauliflower rice from Costco that comes with four packets that each have 4 cups of frozen cauliflower rice. I love how the packets have just the right amount for many recipes, and it’s also much less expensive than most frozen cauliflower rice!

Can you use other vegetables for the cheesy vegetarian casserole?

We loved the combination of broccoli and mushrooms in this casserole, but you can switch out the vegetables for similar amounts of other low-carb veggies your family might prefer.

What cheeses can you use for the vegetarian casserole?

We used a generous amount of sharp cheddar and Monterey Jack cheese to give this veggie casserole plenty of cheesy flavor. Other similar grated cheeses could be used such as Mozzarella, Swiss, Gouda, Colby Jack, or any white cheese that melts well. If you’re not a fan of sharp cheddar you can use mild cheddar or a type of three cheese blend.

Is this Cheesy Vegetarian Casserole low in carbs?

With the changes we made this casserole calculates as 12.5 net carbs and 21 grams of protein per serving, based on 8 servings. But we increased the amounts of most of the ingredients for this updated version, so you might easily get 10 servings out of this recipe, which would make it even lower in carbs.

How to Make Cheesy Vegetarian Casserole (with Cauliflower Rice):

(This is only a summary of the steps for the recipe; please scroll down for complete printable recipe. Or if you use the JUMP TO RECIPE link at the top of the page, it will take you directly to the complete recipe.)

1. 1. Be sure frozen cauliflower rice has thawed.
   2. Preheat oven to 375F/190C. Spray a 9″ x 13″ casserole dish (or similar size) with non-stick spray or olive oil.
   3. Put vegetable broth into saucepan and simmer until it’s reduced to one cup. If you have mushroom base (affiliate link) or mushroom stock cubes (affiliate link) I would add a small amount of that to the vegetable stock . Let stock cool.
   4. Cut up broccoli until you have 6 cups. Microwave broccoli 1 1/2 minutes or until it’s partly cooked but still a bit crisp. Put partly-cooked broccoli into large plastic or glass bowl.
   5. I bought pre-sliced, but wash and slice mushrooms if needed. Heat 1 T olive oil in large frying pan and cook mushrooms until they’re browned and liquid has evaporated. Add mushrooms to bowl with the broccoli.
   6. Chop onion. Heat more olive oil and cook onions until they start to brown; then add Italian Herb Blend and Spike Seasoning cook about a minute more. Add thawed cauliflower rice, mix with onions, and cook about 5 minutes, or long enough to evaporate some of the water.
   7. Add the onions and cauliflower rice to the bowl with the vegetables. Gently mix together broccoli, mushrooms, and onion-cauliflower rice mixture.
   8. Whisk sour cream into the cooled broth, then mix in grated sharp cheddar cheese and 1 cup grated Monterey Jack cheese.
   9. Add sauce mixture to the cauliflower rice mixture and gently combine, until the ingredients are moistened.
   10. Put combined ingredients in the casserole dish, spreading it out.  Sprinkle the other cup of Monterey Jack cheese over the top.
   11. Bake uncovered for about 35 minutes, or until the casserole is bubbly and nicely browned on top.
   12. Serve hot. This will keep for at least a week in the fridge and can be reheated in the microwave or in a pan on the stove.

More Low-Carb Vegetarian Dinners to Try:

• Greek Cauliflower Rice Bake
• Swiss Chard Casserole
• Greek-Style Zucchini Noodles
• Broccoli Cauliflower Rice Casserole
• Peanut Butter Tofu with Sriracha

Weekend Food Prep:

This recipe has been added to a category called Weekend Food Prep to help you find recipes you can prep or cook on the weekend and eat during the week! And this cheesy vegetarian casserole recipe makes 8 generous servings (or 10 side dish servings) so you’ll have some for another day when you don’t want to cook!

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Yield: 8 servings

Cheesy Vegetarian Casserole (with Cauliflower Rice)

Prep Time 45 minutes

Cook Time 35 minutes

Total Time 1 hour 20 minutes

This updated recipe for Cheesy Vegetarian Casserole (with Cauliflower Rice) is a perfect vegetarian main dish or side dish, especially for people who like cheese!

Ingredients

• 4 cups frozen cauliflower rice (see notes)
• one 14 oz. can vegetable broth, simmered to reduce
• 1 T mushroom base (optional, but recommended)
• 1 lb. sliced mushrooms
• 1 medium onion
• 6 cups chopped broccoli
• 2 T olive oil
• 2 tsp. Italian Herb Blend
• 2 tsp. Spike Seasoning (optional but recommended)
• salt and fresh-ground black pepper to taste
• 2 cups sour cream
• 1 cup grated sharp cheddar cheese
• 2 cups grated Monterey Jack cheese

Instructions

1. Be sure frozen cauliflower rice has thawed overnight in the fridge, or thaw for a few hours on the counter
2. Preheat oven to 375F/190C. Spray a 9" x 13" casserole dish (or similar size) with non-stick spray or olive oil
3. Put one can vegetable broth into a small saucepan and let it simmer over medium-low heat until it's reduced to one cup. If you have some mushroom base (affiliate link) or mushroom stock cubes (affiliate link) I would add a small amount of that to the vegetable stock while it simmers. Reducing the stock concentrates the flavor, don't skip that step. Let stock cool
4. Cut up the broccoli into small pieces until you have 6 cups chopped broccoli. Microwave broccoli 1 1/2 minutes or until it's partly cooked but still a bit crisp. (You can cook broccoli in a frying pan for 3-4 minutes if you don't have a microwave.)
5. Put partly-cooked broccoli into large plastic or glass bowl
6. I bought pre-sliced mushrooms that don't need to be washed, but wash and slice mushrooms if needed. Heat 1 T olive oil in large frying pan and cook mushrooms over medium-high heat until they're nicely browned and all liquid has evaporated. Add mushrooms to bowl with the broccoli
7. Chop onion. Heat the rest of the olive oil and cook onions a few minutes until they start to brown; then add the Italian Herb Blend and Spike Seasoning cook about a minute more. Add thawed cauliflower rice, mix with onions, and cook about 5 minutes, or long enough to evaporate some of the water in the cauliflower
8. Add the seasoned onions and cauliflower rice to the bowl with the vegetables
9. Gently mix together the broccoli, mushrooms, and onion-cauliflower rice mixture
10. Whisk the sour cream into the reduced and cooled broth, then mix in the sharp cheddar cheese and 1 cup Monterey Jack cheese
11. Add the sauce mixture to the cauliflower rice mixture and gently combine, until all the ingredients are slightly moistened
12. Put the combined ingredients in the casserole dish, spreading it out so it's even.  Sprinkle the other cup of Monterey Jack cheese over the top.
13. Bake uncovered for 35 minutes, or slightly longer, until the casserole is bubbly and nicely browned on top.
14. Serve hot. This will keep for at least a week in the fridge and can be reheated in the microwave or in a pan on the stove
15. I didn't have any left to freeze, but I am guessing this will freeze pretty well, although the vegetables will definitely be softer after they've been frozen.

Notes

Thaw the frozen cauliflower rice overnight in the fridge or for a few hours on the counter before you use it in this recipe.

I used Better than Bouillon Mushroom Base for this recipe, but you can also use mushroom stock cubes.

Recipe created by Kalyn and Kara.

Nutrition Information:

Yield:

8

Serving Size:

1
Amount Per Serving: Calories: 453Total Fat: 34gSaturated Fat: 18gTrans Fat: 1gUnsaturated Fat: 12gCholesterol: 89mgSodium: 1052mgCarbohydrates: 19gFiber: 6.5gSugar: 7gProtein: 21g

Nutrition information is automatically calculated by the Recipe Plug-In I am using. I am not a nutritionist and cannot guarantee 100% accuracy, since many variables affect those calculations.

Did you make this recipe?

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Low-Carb Diet / Low-Glycemic Diet / South Beach Diet Suggestions:
The updated version of this Cheesy Vegetarian Casserole with Cauliflower Rice would be suitable for low-carb diets, and maybe even Keto if you’re not being too strict on carbs. If it’s made with low-fat sour cream and low-fat cheese, this would be suitable for Phase 2 or 3 of the original South Beach Diet. 

Find More Recipes Like This One:
Use Casseroles to find more recipes like this one. Use the Diet Type Index to find recipes suitable for a specific eating plan. You might also like to follow Danica's Kitchen on Pinterest, on Facebook, on Instagram, on TikTok, or on YouTube to see all the good recipes I’m sharing there.

Historical Notes for this Recipe:
The original version of this recipe that used brown rice was posted in 2014. It updated to a new version that used cauliflower rice and improved with more information in 2023.

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