This easy to prepare cheesy zucchini tomato onion casserole is a delicious way to use up all that fresh garden produce. It’s packed with nutrition, plenty of seasonal flavors and topped with cheesy goodness. Simply slice zucchini, tomatoes and sweet onions, season with garlic, toss in a casserole dish, sprinkle with two kinds of cheese and bake. That’s it! It’s the perfect side dish for any dinner. Oh, and don’t expect to have leftovers – it’s that good! Low carb, gluten-free and keto.
Is there a boatload of zucchini coming out of your garden right now? Are you wondering what to do with it? Well, garden or no, zucchini is at the peak of its season and there’s no better time to make zucchini recipes than now. I’ve already made my death by chocolate zucchini bread, whipped some healthy bran zucchini muffins and baked a savory summer squash galette this season. The galette gave me the inspiration for this casserole. This is an easier preparation with a lot of the same flavors.
You probably know by now that zucchini is one of my favorite vegetables. There’s a good reason for that. Besides its great taste, it’s low in calories, has no saturated fat or cholesterol, is high in fiber and provides potassium, folates and Vitamins A & C. See, aren’t you lovin’ it now too? And it works great as a low carb, gluten-free substitute for pasta in almost any Italian dish like my tasty Zucchini Noodle Carbonara.
But it doesn’t stop there! Zucchini, when used as a side dish, pairs well with almost any meal from chicken to pork to fish. So, come on, why not try this easy zucchini casserole for dinner tonight for some ooey gooey cheesy deliciousness.
Frequently asked questions
Can I make this ahead of time?
You can prep it ahead of time but it is best baked and eaten warm, directly out of the oven.
Can I freeze this casserole?
I wouldn’t advise it. Zucchini is a watery vegetable, so freezing it will make the casserole soggy.
How long will it keep in the refrigerator?
It will easily keep up to 3 days. To reheat, place in the microwave until warmed.
Can I make this into a complete meal?
Absolutely! I sometimes add shredded or chopped up rotisserie chicken or cooked ground beef on top of the zucchini after it is baked and before sprinkling on the cheese.
Gather all the ingredients. Prepare the zucchini by cutting in half then slicing. Dice the tomatoes, slice the onion thinly and grate the cheeses.
- Place all the prepped vegetables in a large bowl along with chopped garlic. (photo 1)
- Season with Italian seasoning, salt & pepper. (photo 2)
- Add olive oil. (photo 3)
- Toss to coat. (photo 4)
- Pour into a greased square baking dish. (photo 5)
- Cover with foil and bake for 30 minutes. (photo 6)
- After the first bake, remove from oven and uncover. (photo 7)
- Sprinkle the cheese over the vegetables. This is a good place to vary it with different flavors of cheese. You can replace the cheddar with Gouda or even Gruyere. (photo 8)
- Make sure to cover well. (photo 9)
- Return to oven and bake uncovered for an additional 30 minutes. Serve immediately. (photo 10)
An easy, delightfully cheesy, side dish that is low carb, gluten free and keto friendly. Believe me, this cheesy zucchini casserole will soon become your family’s new favorite. Enjoy!
More delicious zucchini recipes
Blue Cheese Zucchini Beef Burgers – Yep, it’s a burger packed with plenty of nutritious veggies! It makes the hamburger extra moist and, believe me, no one will be able to tell you snuck some goodies in there.
Zucchini and Prosciutto Skewers – Skewered zucchini and prosciutto are grilled to perfection then served with a lemon basil pesto.
Bruschetta Chicken with Zoodles – makes a light, quick and easy weeknight dinner. Simply brown chicken in a large skillet, add freshly made bruschetta, toss in some zoodles and it’s ready!
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Cheesy Zucchini Tomato Onion Casserole
- 2 zucchini, washed & halved lengthwise then cut into slices
- 1 large tomato, cubed
- 1 medium sweet onion, sliced thin, then halved
- 6 garlic cloves, chopped
- 1 teaspoon Italian seasoning
- Salt & pepper to taste
- 1 1/2 cup cheddar cheese, shredded
- 1/2 cup Pecorino Romano or Parmesan, grated
- Preheat oven to 375 degrees. Lightly coat an 8x8-inch baking dish with olive oil.
- Prepare vegetables by cutting zucchini in half lengthwise then slicing. Dice tomato and slice onion thinly.
- In a large bowl, toss the vegetables together with Italian seasoning and salt and pepper to taste.
- Place in prepared baking dish and drizzle a little more olive oil over vegetables. Cover with foil and bake for 30 minutes.
- While zucchini is baking, grate both cheeses.
- Remove casserole from oven, uncover, and sprinkle cheeses over top of vegetables.
- Place back in oven and bake, uncovered, for another 30 minutes.
Frequently asked questionsCan I make this ahead of time? You can prep it ahead of time but it is best baked and eaten warm, directly out of the oven. Can I freeze this casserole? I wouldn't advise it. Zucchini is a watery vegetable, so freezing it will make the casserole soggy. How long will it keep in the refrigerator? It will easily keep up to 3 days. To reheat, place in the microwave until warmed. Can I make this into a complete meal? Absolutely! I sometimes add shredded or chopped up rotisserie chicken or cooked ground beef on top of the zucchini after it is baked and before sprinkling on the cheese.
This post has been updated with new photos and step-by-step directions. It was first published on June 7, 2015.