Easy Baked Zucchini, Tomato and Mozzarella Gratin

There is nothing quite like the rich aroma of summer vegetables roasting alongside fragrant herbs and melting cheese to bring the warmth of the Mediterranean straight into your kitchen. This Baked Zucchini, Tomato and Mozzarella Gratin is a stunning, flavorful dish born from the harmonious marriage of two sun-drenched culinary traditions: the rustic Provençal vegetable tian of southern France and the iconic Caprese salad of southern Italy. As the vegetables bake, the sweet acidity of ripe tomatoes softens the mild, delicate crunch of fresh zucchini, while rich mozzarella melts into every crevice to bind the dish together.

Visually, this gratin is an absolute showstopper on any dining table. Layered in a rustic, oval ceramic baking dish, alternating wheel-like rounds of deep green zucchini, vibrant red tomatoes, and molten, golden-brown mozzarella slices create an eye-catching pattern. Finished with a drizzle of emerald-green basil pesto that pools gently around the vegetables, this recipe proves that beautiful cooking does not have to be complex.

At its core, this recipe is an effortless celebration of peak summer produce, heart-healthy extra virgin olive oil, and fresh garden herbs. Whether you are hosting a weekend dinner party or putting together a quick weeknight meal, this recipe captures the essence of wholesome, sun-ripened Mediterranean dining with minimal effort.

Why You’ll Love This Mediterranean Gratin

• Naturally Low-Carb & Vegetarian: Unlike traditional heavy casseroles that rely on white flour roux, breadcrumb fillers, or heavy cream, this dish lets fresh summer vegetables and healthy fats take center stage.
• Vibrant Caprese & Tian Fusion: You get the best of both worlds—the warm, slow-roasted sweetness of a French vegetable tian combined with the rich, aromatic basil-and-mozzarella profile of a classic Italian Caprese.
• Crowd-Pleaser Side Dish: Its versatile flavor profile makes it an ideal pairing for almost any protein, from grilled seafood to roasted poultry.
• Simple 15-Minute Active Prep: Fast slicing and assembling are all it takes before your oven steps in to do the heavy lifting.

Ingredients & Smart Mediterranean Substitutions

Creating an exceptional Baked Zucchini, Tomato and Mozzarella Gratin relies heavily on sourcing fresh, high-quality ingredients. Because this dish highlights simple whole foods, each element plays an essential role in the final flavor profile.

• Zucchini: You will need 2 medium zucchinis, sliced into uniform 1/4-inch rounds. Tip: Look for firm, medium-sized zucchini with smooth, unblemished dark green skin. Smaller to medium zucchini have fewer seeds and lower water content than oversized ones. There is no need to peel them—the skin provides structure, vibrant color, and valuable fiber.
• Ripe Tomatoes: Choose 3 to 4 ripe Roma or vine-ripened tomatoes, sliced into 1/4-inch rounds. Tip: Roma tomatoes are the absolute best choice for baking because they have dense flesh, fewer seeds, and significantly less liquid than beefsteak varieties.
• Fresh Mozzarella Cheese: Use 8 oz of fresh mozzarella, either sliced into rounds or thickly shredded. Mediterranean Tip: Fresh mozzarella offers a mild, creamy contrast to the bright acidity of the tomatoes. To ensure your gratin gets a beautiful golden top without excess pooling, pat the mozzarella slices dry with paper towels before layering.
• Extra Virgin Olive Oil (EVOO): You’ll use 1 tablespoon for greasing the baking dish, plus an extra drizzle over the top. Tip: Always choose high-quality, cold-pressed Extra Virgin Olive Oil to accentuate the authentic Mediterranean diet profile and add rich, peppery depth.
• Prepared Basil Pesto: 1/2 cup of basil pesto (store-bought or homemade). Tip: Pesto acts as an all-in-one flavor catalyst, instantly infusing the dish with garlic, fresh basil, pine nuts, and olive oil without requiring individual chopping.
• Parmesan Cheese (Optional): 1/4 cup of freshly grated Parmesan cheese scattered across the top creates an extra savory, nutty, and golden-brown outer crust.
• Salt & Freshly Ground Black Pepper: Essential seasonings that heighten the natural sweetness of the tomatoes and help draw out unwanted moisture during prep.
• Crusty Bread (For Serving): Whole-grain sourdough or rustic artisan bread is perfect for scooping up the fragrant, savory juices left at the bottom of the baking dish.

The Secret to a Non-Watery Zucchini Gratin (The 3-Step Fix)

The single most common complaint cooks have when making a Baked Zucchini, Tomato and Mozzarella Gratin is an excess accumulation of liquid at the bottom of the dish. Because both zucchini and tomatoes are composed of over 90% water, baking them without proper prep can steam the vegetables instead of roasting them. Follow this tried-and-true 3-step method to guarantee a rich, concentrated gratin every single time:

1. The 15-Minute Salt Sweat: Arrange your sliced zucchini and tomato rounds in a single layer over paper towels or a clean kitchen towel. Sprinkle them lightly with kosher salt and allow them to sit undisturbed for 15 minutes. The salt draws out surplus surface water through osmosis.
2. Pat Dry: Once the 15 minutes have passed, take additional paper towels and firmly press down on top of the sliced vegetables. You will be amazed at how much moisture transfers onto the towel before assembling.
3. Select the Right Tomato & Bake Uncovered: Stick to firm Roma tomatoes, which naturally contain less seed jelly. Furthermore, always bake your gratin uncovered at 375°F (190°C). Cooking without a foil cover allows steam to evaporate freely, leaving behind a perfectly thick, bubbly casserole.

How to Make Baked Zucchini, Tomato and Mozzarella Gratin (Step-by-Step)

Follow these simple steps to assemble and bake your gratin:

Step 1: Prep the Oven & Dish

Preheat your oven to 375°F (190°C). Generously grease the bottom and sides of a medium oval or rectangular ceramic baking dish with 1 tablespoon of extra virgin olive oil.

Step 2: Shingle the Layers

Take your pre-salted and dried vegetable and cheese slices. Arrange them vertically at a slight angle along the length of the dish, alternating in a repeating pattern: zucchini round $\rightarrow$ tomato slice $\rightarrow$ mozzarella slice. Continue this shingling process until the entire baking dish is tightly packed with vibrant rows.

Step 3: Season & Drizzle Pesto

Lightly sprinkle freshly ground black pepper over the arranged rows (hold off on adding extra salt, as the vegetables were pre-salted). Spoon the prepared basil pesto evenly over the top, allowing it to pool naturally into the crevices between the cheese and vegetables.

Step 4: Top with Parmesan (Optional)

If you enjoy an extra crisp, savory topping, scatter the freshly grated Parmesan cheese evenly over the pesto and mozzarella layer.

Step 5: Bake to Golden Perfection

Transfer the dish into your preheated oven and bake uncovered for 25 to 30 minutes. You will know it is ready when the vegetables are tender when pierced with a fork, and the mozzarella is completely melted, bubbling, and beautifully browned around the edges.

Step 6: Rest Before Serving

Remove the gratin from the oven and let it rest undisturbed for 5 to 10 minutes. Resting allows the melted cheese and natural juices to settle and thicken slightly, making the gratin easy to scoop and serve alongside warm, rustic sourdough bread.

Mediterranean Diet Benefits

Integrating this Baked Zucchini, Tomato and Mozzarella Gratin into your weekly routine is an easy way to embrace the longevity-boosting benefits of the traditional Mediterranean diet:

• Antioxidant-Rich: Cooking tomatoes significantly increases the bioavailability of lycopene, a potent antioxidant linked to heart health and reduced cellular inflammation. Combined with the polyphenols in extra virgin olive oil, this dish delivers a powerful nutrient punch.
• Micronutrient Dense: Fresh zucchini and basil supply an abundance of essential micronutrients, including Vitamin C, Vitamin A, Potassium, and Dietary Fiber, supporting immune defense and healthy digestion.
• Heart-Healthy Fats: Rather than relying on heavy butter sauces or artificial additives, this recipe uses cold-pressed extra virgin olive oil and nutrient-dense pine nuts (via the basil pesto) to provide heart-healthy monounsaturated fats.

What to Serve with This Vegetable Gratin

This colorful vegetable bake serves as an exceptionally versatile side dish that complements a wide array of Mediterranean main courses. Try pairing it with these wholesome options:

Proteins

For a complete, protein-packed meal, serve this gratin alongside our tender Spinach and Feta Stuffed Salmon Recipe or a vibrant platter of Garlic Herb Roasted Chicken and Vegetables. It also pairs wonderfully with baked garlic butter shrimp or pan-seared white fish.

Grains

Accompany the gratin with a side of herbed quinoa, lemon-infused brown rice pilaf, or a thick slice of warm, whole-grain sourdough bread to mop up the herbaceous olive oil juices.

Salads

Balance the warm, melty comfort of the gratin with a crisp, refreshing salad like our classic Greek Chopped Feta Salad recipe. The crunch of fresh cucumbers and tangy olives offers a fantastic contrast.

Storage, Meal Prep & Reheating

• Storage: Allow any leftover gratin to cool completely to room temperature. Transfer leftovers into an airtight glass container and store in the refrigerator for up to 3 days.
• Reheating: To maintain optimal texture, reheat leftovers in a preheated oven or toaster oven at 350°F (175°C) for 10 to 12 minutes until warmed through and bubbly.
• Avoid Microwaving: Microwaving is not recommended, as it causes fresh mozzarella to turn rubbery and causes the vegetables to release trapped moisture, leaving you with a watery base.

Frequently Asked Questions (PAA & SEO FAQs)

Q1: Do I need to peel zucchini before baking in a gratin?

Answer: No, peeling is completely unnecessary! Leaving the skin intact helps the zucchini slices maintain their structural integrity so they don’t turn mushy while baking. Additionally, the dark green peel adds beautiful visual contrast, valuable dietary fiber, and essential nutrients.

Q2: Can I make this zucchini tomato gratin ahead of time?

Answer: Yes! You can slice, salt, and pat dry the vegetables up to 1 day in advance. You can also fully assemble the tiled vegetable and cheese layers in your baking dish up to 4 hours ahead of time. Cover the dish tightly with plastic wrap and store it in the refrigerator. Drizzle with pesto and add Parmesan right before popping it into the oven.

Q3: What is the difference between a tian, casserole, and gratin?

Answer: A tian refers specifically to a French dish of finely sliced vegetables layered tightly and baked slowly. A gratin is a culinary technique where a dish is topped with a golden-brown crust (traditionally achieved using cheese, breadcrumbs, or butter). A casserole is a broad, overarching term for any meal baked slowly in a deep dish. This recipe combines tian-style layering with a traditional gratin cheese finish.

Q4: Can I use dried herbs instead of pesto?

Answer: Absolutely. If you don’t have basil pesto on hand, simply whisk 2 tablespoons of extra virgin olive oil with 1 teaspoon of dried oregano, 1 teaspoon of dried basil, and 1 finely minced garlic clove. Drizzle this herb mixture evenly across the layered vegetables before baking.