High-Protein Low-Calorie Tuna Zucchini Casserole

1 h 15 min | easy | clean eating, gluten-free, high-protein, Mediterranean diet

Baked tuna zucchini casserole in a white rectangular baking dish, topped with melted golden cheese and visible curls of green and yellow zucchini noodles on a white wooden surface.

Published Apr 16, 2026

Prep Time	Cook Time	Total Time
45 min	30 min	1 h 15 min

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Introduction

This high-protein, low-calorie tuna zucchini casserole is creamy, cheesy, and light enough for an easy weeknight dinner.

With spiralized zucchini, tuna, and cottage cheese, it is a family-friendly meal that also works for meal prep lunches.

Serving of tuna zucchini casserole on a gray plate, with spiralized zucchini noodles, flaky tuna, and melted browned cheese, sprinkled with chopped herbs; the baking dish appears blurred in the background.

How to Make High-Protein Low-Calorie Tuna Zucchini Casserole

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Dry the zucchini noodles

Spiralize the zucchini, then spread the noodles on paper towels and lightly salt them if you like.
Let them sit for 30 minutes, then blot well so the casserole stays creamy instead of watery.
Mix the filling

Heat the oven to 375°F and grease a medium baking dish.
In a large bowl, stir together tuna, cottage cheese, egg, yogurt, garlic powder, onion powder, salt, and pepper.

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Combine and assemble

Fold in the zucchini noodles and half the mozzarella until everything looks evenly coated.
Transfer the mixture to the dish, then top with the remaining mozzarella and Parmesan.
The zucchini keeps this casserole low-carb while still giving it a cozy noodle-like feel.
Bake until set

Bake for 25 to 30 minutes, until the center is hot and the cheese is melted.
Broil for 1 to 2 minutes if you want a deeper golden top.
Rest and serve

Let the casserole rest for 10 minutes before serving so the slices hold together better.
This brief rest also helps picky eaters enjoy a less watery, more familiar texture.

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Close-up of baked tuna zucchini casserole in a white dish, with spiralized zucchini noodles curled through melted mozzarella, browned cheesy spots, flaky tuna pieces, and a sprinkle of herbs on top.

Substitutions

Tuna for canned salmon: Canned salmon keeps the protein high and adds a richer flavor. The casserole stays moist and still bakes up gently.
Zucchini noodles for yellow squash noodles: Yellow squash noodles keep the dish low-carb and cook at the same pace. They bring a slightly sweeter flavor and the same tender texture.
Mozzarella for reduced-fat cheddar: Reduced-fat cheddar adds sharper flavor and a firmer top. The casserole stays cheesy, and the browned edges taste especially savory.

Tips

Dry the zucchini well: Zucchini releases water as it bakes. Resting and blotting the noodles first keeps the filling creamy and sliceable.
Drain the tuna completely: Even a little extra liquid can loosen the casserole. Press the tuna against the can lid before adding it.
Use a shallow baking dish: A shallow dish helps moisture evaporate faster. It also gives you more browned cheese across the top.
Let it rest before serving: A short rest helps the proteins set. You will get cleaner scoops and a better casserole texture.

Nutrition Facts ^*

Energy	198	kcal
Protein	26	g
Total Fat	8	g
Carbohydrates	8	g
Dietary Fiber	2	g

^* Approximate, per serving.
Data source: USDA FoodData Central.

FAQ

Why did my casserole turn out watery?: The zucchini likely held too much moisture, or the tuna was not drained enough. Let the noodles rest, blot them well, and bake in a shallow dish.
Can I make this casserole ahead of time?: Yes. Assemble it, cover it, and refrigerate it for up to one day before baking. Add a few extra minutes if the dish goes into the oven cold.
How do I know when it is done baking?: The center should look set, not loose, and the cheese should be fully melted. A thermometer should read 165°F in the middle.
Can I use sliced zucchini instead of spiralized zucchini?: Yes. Thin half-moons work well, but they release a bit more water. Salt, rest, and blot them before mixing.

Serving Suggestions

Fresh basil or chopped parsley adds color and a clean finish to the rich, cheesy filling.

A crisp green salad or roasted broccoli makes this low-carb dinner feel complete without extra heaviness.

For a more comfort-food style pan, add red pepper flakes or a few chopped sun-dried tomatoes.

Recipe by Eunice.
“I learned to cook by standing in my grandma’s kitchen, watching her turn simple ingredients into meals that fed our entire family. That’s where it started. Today, I create recipes for real life, real kitchens, and anyone who wants good food without overthinking it.” Read more.