Baked zucchini tomato casserole is an easy summer side dish made with layers of fresh zucchini, ripe tomatoes, shallots, garlic, thyme, and a crisp Parmesan breadcrumb topping. Inspired by a French vegetable tian, this light casserole pairs well with grilled chicken, steak, fish, or pork and can be made gluten-free with gluten-free breadcrumbs.
This recipe is inspired by a French vegetable tian, a simple Provençal dish of layered summer vegetables baked until tender. My version keeps it light and fresh, then adds shallots, garlic, thyme, Parmesan, and a crisp breadcrumb topping for extra flavor and crunch without making it heavy.
Zucchini Tomato Casserole Snapshot
- A great way to use summer zucchini and tomatoes - Perfect for garden produce and farmers market finds.
- Easy baked side dish - Simple ingredients and minimal prep.
- Light, not heavy - No cream sauce, just olive oil, garlic, herbs, and a crisp Parmesan topping.
- Make-ahead friendly - Assemble ahead and bake when ready.
- Pairs with almost anything - Great with grilled chicken, steak, pork, fish, or burgers.
Ingredients You'll Need
- Tomatoes - Use Roma tomatoes because they're meaty and less watery, preventing a soggy zucchini tomato casserole.
- Zucchini - Choose zucchini close in diameter to the tomatoes for even layering and a prettier baked casserole.
- Shallots - Add mellow, sweet flavor that's softer than onion.
- Parmesan cheese - Parmigiano-Reggiano adds savory depth and helps create a golden, crisp topping.
- Breadcrumbs - Use gluten-free or regular breadcrumbs. They add crunch and structure to the Parmesan topping.
- Fresh thyme - Adds an earthy, aromatic note that pairs beautifully with tomatoes and zucchini.
- Garlic - Adds a punch of flavor. Chop it finely or use a microplane zester.
- Extra virgin olive oil - Adds flavor, helps coat the vegetables, and encourages browning on top.inish the top for browning.
Please see the recipe card for measurements, salt, and pepper.
Chef's Tip: Homemade breadcrumbs give this zucchini tomato casserole a better, crisper topping than most store-bought crumbs. Use gluten-free or regular bread, pulse into coarse crumbs, and toast lightly before using for the best texture. Here's how to make homemade breadcrumbs.
Substitutions and Variations
- Herbs - Swap fresh thyme for fresh oregano, or use dried Herbes de Provence for more Provençal flavor.
- Cheese - Parmesan is classic, but Pecorino Romano adds a saltier bite. For dairy-free, skip the cheese or use your favorite vegan Parmesan-style topping.
- Add-ins - Add a few thin slices of eggplant or yellow squash to the layers for more summer vegetable flavor.
How to Make Zucchini Tomato Casserole
Use either an oval casserole baking dish called a gratin, oval roaster, or a rectangular baking dish. Use a 3-4 quart size. The dish in the photo is approximately 13" long, 10" wide and 2 ½ " deep. For a rectangular casserole, arrange the vegetables in rows rather than an oval.
Slice the tomatoes and zucchini crosswise into about ¼" thick circles. Sauté shallot and garlic in olive oil until soft and place it in the bottom of the casserole, then top with overlapping layers of tomatoes and zucchini.
Pack the slices fairly tight as they shrink during baking. Sprinkle the topping over the top and bake uncovered until golden, about 35-45 minutes. Serve to the happy smiles of your family.
Serving Suggestions
- As a side dish - Serve alongside grilled chicken, seared fish, or pork roast for a Provençal-inspired meal.
- With pasta or grains - Spoon over cooked quinoa, couscous, or polenta for a simple vegetarian main.
- For brunch - Pair with soft scrambled eggs or a poached egg on top and crusty bread on the side.
Another idea for summer tomatoes is tomato gazpacho soup. It's cool, refreshing and delicious!
📖 Recipe
Zucchini Tomato Casserole
Equipment
- casserole baking dish
Ingredients
- 6 Roma tomatoes about 1 ¼ pounds
- 3 zucchini about ¾ - 1 pound
- ¾ cup sliced shallots 1 large shallot
- ⅓ cup grated parmesan cheese
- 3 tablespoons breadcrumbs GF or wheat, as needed
- 1 ½ tablespoons fresh chopped thyme leaves
- 3 large garlic cloves finely chopped or zested
- ⅛ teaspoon sea salt
- ⅛ teaspoon ground black pepper
- 2 tablespoons extra virgin olive oil divided use
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Instructions
Prep vegetables
- Pre-heat an oven to 375° degrees. Slice tomatoes and zucchini crosswise into approximately ¼" slices.
Cook shallot and garlic
- Add 1 tablespoon of olive oil to a small pan and heat oil over medium low heat. Add the shallot and cook until soft, about 2-3 minutes. Add garlic and cook another 30-60 seconds. Spread the soft shallots and garlic into the bottom of a 3-4 quart oval casserole.
Layer the vegetables
- Layer the tomato and zucchini slices alternately around the dish, starting at the outside and working in, overlapping tightly. Get as much as you can into the dish. You may not use quite all of the slices. Sprinkle with the salt and pepper.
Create topping
- Combine the parmesan, breadcrumbs, and herbs (or dairy-free sprinkle) then then scatter evenly over the top of the casserole. Drizzle with the last tablespoon of the olive oil.
Bake casserole
- Bake casserole until top is golden and crisp, about 35-45 minutes. Timing will depend on your oven. Serve warm.
Notes
Dairy-Free Cheesy Sprinkle (Parmesan Alternative)
- ½ cup raw, unsalted cashews
- 3 tablespoons nutritional yeast (Sari or Bragg)
- ¾ teaspoon granulated garlic (or ½ teaspoon garlic powder)
- ½ teaspoon fine sea salt (adjust to taste)
- Add all ingredients to a food processor or high-speed blender.
- Pulse until it forms a fine, crumbly texture like grated Parmesan-don't over-blend or it'll turn into a paste.
- Taste and adjust salt or garlic to preference.
- Store in an airtight jar in the fridge for up to a month.
Nutrition
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Debbie in Alaska says
Do you think you could do this in a crockpot???
Sally Cameron says
Hi Debbie. I don't think a crock pot would work. This is an oven kind of recipe.
Denise says
Perfect! It looks delicious! I am testing different yeast powder for a best taste. I bought one that I didn't like at all. It smells bad! What brand are you using?
Sally Cameron says
Hi Denise. I bought it on Amazon, Sari Foods. Non-GMO, no synthetic vitamins, organic, really good. Think I put the link in the post. I will check the post right now for the cheesy sprinkle...