Healthy Zucchini Tomato Casserole – Zucchini Tomato Onion Casserole

Healthy Zucchini Tomato Casserole includes a menagerie of fresh garden veggies sautéed together. Before serving this zucchini, tomato and onion casserole, a layer of shredded Parmesan cheese is melted over top for the perfect finishing touch.

Healthy Zucchini Tomato Casserole Recipe

It’s simple to eat healthier during the summer when garden vegetables are fresh and bountiful. I love combining all that I have in the vegetable drawer and making a tasty garden veggie casserole, which is exactly what drew me into this recipe from my North Carolina Elks Association cookbook.

• Zucchini
• Tomatoes
• Green Peppers
• Red Onion

All these veggies get sautéed in butter, seasoned with salt and black pepper, and then topped with Parmesan cheese before being finished off in the oven. When the casserole is bubbling, the vegetables are lightly browned, the cheese is melted, and the kitchen smells heavenly, you’ll know these sautéed Parmesan vegetables are ready to eat.

Zucchini Tomato Onion Casserole

Fresh, garden tomatoes tend to be juicy which result in a delightful saucy zucchini tomato onion casserole. I recommend grabbing some bread and butter and sopping up that juice. (This is exactly how our Grandpa would have eaten it). Or, try serving it over cooked rice which also absorbs the tasty sauce.

But, if you prefer less saucy tomato, onions and zucchini, then go ahead and peel and de-seed the tomatoes before adding to the skillet.

If you have an abundance of tomatoes, try these Broiled Tomato Slices!

Ingredient List for Garden Casserole

• Green Peppers, sliced
• Onions, diced
• Butter
• Tomatoes, cut into wedges
• Salt
• Black Pepper
• Parmesan Cheese, shredded

How to Make Zucchini, Tomato and Onion Recipe

Step By Step Instructions

1. Preheat oven to 375 degrees F.
2. Sauté green peppers and onions in butter until just softened.
3. Add diced zucchini, and sauté for 5 minutes.
4. To the skillet, add tomato wedges, and continue to cook for 5 minutes or until tomatoes are soft.
5. Season generously with black pepper and salt.
6. Pour into a greased baking dish. Top with shredded Parmesan cheese.
7. Bake in a preheated oven for 15-20 minutes or until the top browns and the cheese melts.
8. Let zucchini tomato bake sit for 10 minutes before serving.

Storage Instructions

Let leftovers cool completely. Store leftovers in an airtight container in the fridge for 3 – 5 days.

For the full recipe steps and ingredient amounts for Sautéed Zucchini and Tomatoes, scroll to the bottom of this post. 

Recipe FAQs

• Substitute white or yellow onions for purple, if desired.
• Use olive oil to sauté your veggies instead of butter if you wish.
• If you are looking for a really cheesy zucchini tomato casserole, add extra Parmesan cheese!
• Be sure to let the zucchini casserole sit on the counter for 10 minutes before serving to let it cool and thicken slightly.
• The original recipe calls for the tomatoes to be peeled. If you prefer to go this route, go for it!
• Want a stove top version with chicken? Try our Chicken with Tomatoes and Zucchini recipe.
• I like the extra liquid in this zucchini onion and tomato bake; however, you can remove the seeds and liquid from the tomato before sautéing. This will result in a thicker casserole.
  • I like to sop up the extra juices with a piece of bread and butter, just like Grandpa would do.  Or, sometimes I serve over cooked rice.

Recipe Variations

• Use any type of onions and tomatoes.
• Omit onions, and use onion powder instead.
• Add minced garlic or garlic powder.
• If you are completely out of fresh tomatoes, use a can of stewed tomatoes, diced tomatoes or tomato sauce.
• Substitute mozzarella cheese for Parmesan cheese.
• Add herbs such as oregano or basil.
• Garnish with herbs such as fresh basil or fresh parsley.

Are you supposed to remove seeds from zucchini?

If your zucchini is small to medium in size, then the seeds will be ok to use in cooking or baking; however, once the zucchini gets large, it will also have large, annoying seeds. To remove seeds, cut in half lengthwise. Take a spoon and scoop out the large seeds. Discard the seeds.

Should you salt zucchini before you cook it?

Zucchini does not need to be salted before cooking.

Why does zucchini get soft when cooked?

Zucchini naturally have a high water content which is why the texture becomes soft when cooked.

Do you peel zucchini to eat it?

The skins of zucchini are thin and edible. There is no need to peel zucchini before eating or cooking. Safe yourself some time by leaving the peel intact.

What vegetables go good with zucchini?

Zucchini have a very mellow, slightly bland flavor. This means that zucchini can be paired with almost any other vegetables. I love mixing zucchini with yellow squash for endless casseroles. Zucchini is also great along side fresh, garden tomatoes in the summer. Zucchini is also a great addition to vegetable soup to make it stretch and feed more mouths.

More Zucchini Casserole Recipes

Old Fashioned Cheesy Zucchini Casserole

Zucchini with Tomatoes and Bacon

Sour Cream Zucchini Casserole

Layered Zucchini Casserole with Ground Beef

Breakfast Casserole with Zucchini