Parmesan Zucchini and Tomato Gratin
When zucchini and tomatoes are at their peak, this zucchini tomato gratin is exactly what I make. It’s a simple baked zucchini tomato casserole layered with tender zucchini, juicy tomatoes, garlic, and golden Parmesan — light, flavorful, and perfect for weeknight dinners or entertaining. Save This Recipe Enter your email and we’ll send the recipe directly to you! By submitting this form, you consent to receive emails from Delicious Meets Healthy. If you’ve ever grown zucchini and tomatoes, you know how quickly they take over the kitchen. Every summer, our vegetable garden gives us an abundance of garden-fresh vegetables, especially zucchini, squash, and tomatoes — and this zucchini tomato gratin is one of the first dishes I make on repeat. I’ve tweaked the layering and seasoning over the years until it became the perfect balance of tender vegetables and a lightly golden, cheesy top. It’s light enough for warm summer evenings, yet cozy enough to serve year-round. If you have more zucchini than you know what to do with them, have you checked out my Stuffed Zucchini Boats with Yogurt Garlic Sauce and my Stuffed Zucchini Cups? Key Ingredients (With Helpful Notes) Here’s what you’ll need. I’m also sharing a few insights from my own kitchen testing to help you get the best results. Yellow onion – Adds sweetness and depth. Don’t skip sautéing — it prevents sharp, raw onion flavor. Garlic – Fresh garlic makes a huge difference here. Pre-minced works in a pinch, but I prefer freshly minced for aroma. Zucchini – Slice thinly and evenly. If they’re too thick, they won’t cook through evenly. Tomatoes – I prefer Roma (plum) tomatoes or other firm, meaty varieties like Campari or vine-ripened tomatoes. They hold their shape beautifully while baking and help prevent the zucchini tomato gratin from becoming watery. I recommend avoiding overripe, soft, or mushy tomatoes, as well as large beefsteak varieties with high water content, since they can release too much liquid and make the casserole soggy. Parmesan cheese – I always grate my own for better melting and flavor. Pre-shredded can work, but it doesn’t melt as smoothly. Oregano – Adds that classic Mediterranean flavor. You can use fresh or dried.Optional Add-Ins (if you want to elevate it): I occasionally mix breadcrumbs with the Parmesan before baking for added golden crunch, or finish the gratin with a drizzle of fresh basil pesto for bright Mediterranean flavor. How to Make Zucchini Tomato Gratin I’ve tested this recipe enough times to know that keeping it simple is what makes it foolproof. Just four straightforward steps — that’s it. Preheat & Sauté the Aromatics. Preheat your oven. Heat olive oil in a skillet over medium heat. Sauté the onion until soft and translucent, then add the garlic and cook just until fragrant. Don’t skip this step — gently softening the onion builds natural sweetness and depth, while the sautéed garlic adds rich, savory flavor to the zucchini tomato gratin. Create the Flavor Base. Spread about one-third of the onion and garlic mixture over the bottom of your baking dish. I’ve found this not only prevents sticking but also ensures every bite of this zucchini tomato gratin has flavor from the bottom up. Layer, Season & Finish. Arrange the zucchini and tomato slices in an alternating, slightly overlapping pattern until the dish is filled. Top with the remaining onion mixture. Drizzle with olive oil, season with salt, pepper, and oregano, and sprinkle evenly with Parmesan. Tip from my kitchen: Layer them snugly — they shrink as they bake. Bake & Rest. Bake until the vegetables are tender and the top is lightly golden. Let the zucchini tomato casserole rest briefly before serving so the juices settle and slicing is easier. TIPS FROM NELI’S KITCHEN My Top Tips for a Perfect Zucchini Tomato Casserole After making this many times, here are my tried and true recipe notes: Slice evenly. Uneven slices cook unevenly. Use firm tomatoes. Too juicy = soggy casserole. Salt lightly between layers if your tomatoes are mild. Let it rest before serving. This reduces excess moisture. Don’t overload with cheese. This dish is about vegetables first, cheese second. If you struggle with watery zucchini dishes, you can lightly salt the zucchini slices and let them sit for 10 minutes, then pat dry before layering. I only do this when the zucchini are especially fresh and moist. Serving Suggestions This baked zucchini tomato gratin is incredibly versatile. Here’s how I love serving it: Alongside grilled chicken or fish As part of a Mediterranean-style spread With a simple arugula salad Over cooked quinoa or pasta for a light vegetarian main Sometimes I even serve leftovers with a fried egg on top for brunch — highly recommend. You can serve this gratin as a side with baked or grilled chicken, meat skewers, fish, etc. It’s a perfect side dish for summer when tomatoes and zucchini are in abundance. It also makes a great side dish to bring to a potluck or a family gathering. Storing and Reheating If you happen to have leftovers, here are my suggestions: Storing: Let the zucchini tomato gratin cool completely, then refrigerate in an airtight container for up to a few days. Reheating: For the best texture, reheat in the oven until warmed through — this helps maintain that lightly golden top. You can microwave it for convenience, but it will be softer. More Zucchini Recipes: Zucchini Lasagna Roll-Ups Stuffed Zucchini Cups Stuffed Zucchini Boats Zucchini Soup Prep Time: 15 minutes minutes Cook Time: 35 minutes minutes Total Time: 50 minutes minutes Servings: 6 Save This Recipe Enter your email and we’ll send the recipe directly to you! By submitting this form, you consent to receive emails from Delicious Meets Healthy. Cook ModePrevent your screen from going dark Preheat your oven to 350°F. Heat 1 tablespoon olive oil in a small skillet over medium heat. Add the chopped onion and sauté until soft and translucent, about 3–4 minutes. Stir in the garlic and cook…
