Baked Ratatouille Casserole

This baked ratatouille casserole is a vibrant celebration of Mediterannean flavors brought to your weeknight table with ease. Thin rounds of zucchini, yellow squash, eggplant, and tomato nestle into a richly seasoned marinara base enhanced with garlic, herbs, and vegetable bouillon. It bakes into tender layers with caramelized edges, perfectly suited for a meatless main, a side dish, or a makeahead crowd pleaser.

When I first made this casserole, the layered presentation and fragrant aroma kept everyone at the table eager to dive in. Now it’s a regular request for potlucks and cozy dinners alike.

Ingredients

• Zucchini: sliced thin for tender texture and vibrant green color
• Yellow squash: sliced the same thickness to match zucchini and keep cooking even
• Eggplant: ideally a slender Japanese or Italian variety, ensures uniform layers and prevents bitterness
• Tomatoes: sliced thin add juiciness and bright acidity to balance richness
• Red bell pepper: optional for added sweetness and color contrast
• Marinara sauce: forms a savory, saucy base that carries herbs and umami
• Olive oil: for brushing, helping flavors to meld and edges to caramelize beautifully
• Granulated vegetable bouillon: dissolved in water boosts depth and rounds flavor without adding wateriness
• Minced garlic: infuses aromatic warmth throughout the layers
• Dried thyme and oregano: for authentic Mediterranean herby notes
• Salt and freshly ground black pepper: to season and elevate all components

Instructions

Heat the oven and prep the dish:

Preheat your oven to 375 degrees Fahrenheit. Lightly oil a 9 inch round or similar sized baking dish to prevent sticking and aid in browning.

Choose the right eggplant and slice evenly:

Select a thin, long eggplant such as Japanese or slender Italian. This ensures the rounds will match the zucchini and yellow squash in size and thickness, creating neat, even layers. Use a sharp knife or mandoline to slice the eggplant, zucchini, yellow squash, tomatoes, and optional red bell pepper into rounds about one eighth of an inch thick. Uniform slices help everything cook evenly.

Lay vegetables flat and season first:

Arrange all the vegetable slices flat on a sheet pan or cutting board. Sprinkle evenly with thyme, oregano, black pepper, and salt. Allow them to rest for 10 to 15 minutes. This pulls out surface moisture, resulting in a deeper roasted flavor and preventing watery casserole.

Brush on garlic olive oil:

Stir the minced garlic into two tablespoons of olive oil. Lightly brush both sides of each vegetable slice with this mixture. This step adheres the seasoning and infuses garlic flavor into every layer.

Build the saucy base:

Dissolve the vegetable bouillon granules in two tablespoons of hot water until fully smooth. Stir this mixture into the marinara sauce. Taste the marinara base to decide if additional salt is needed as bouillon can vary in saltiness. Spread the marinara evenly on the bottom of your baking dish.

Assemble the casserole:

Stand the seasoned veggie rounds upright and snugly close together in a repeating color pattern over the marinara base. Pack the slices tight to avoid spaces where steam could make the dish watery. Drizzle the remaining tablespoon of olive oil over the top. This encourages a shiny, roasted finish.

Bake to tender perfection:

Cover the baking dish with a parchment paper sheet tucked just over the vegetables before placing foil on top. The parchment prevents sticking while the foil traps steam, allowing the vegetables to soften without drying. Bake covered for 35 minutes. Then remove the cover and bake uncovered for another 15 to 20 minutes until the vegetables are very tender and the edges caramelize lightly. Let the casserole rest for 10 minutes so the juices thicken and settle.

Make it fully vegan and gluten free:

Choose marinara without cheese and check that your vegetable bouillon is certified gluten free or substitute gluten free chickpea miso. Avoid dairy or wheat based toppings to keep the casserole suitable for all diets.

My favorite part is how the vegetable layers come together after baking, with edges that caramelize to a sweet, smoky finish. I treasure making this dish with family on weekends when we gather and share stories while the kitchen fills with the aroma of herbs and garlic.

Storage Tips

Store leftovers uncovered or lightly covered in the refrigerator for up to four days. Reheat gently in the oven at 325 degrees Fahrenheit to preserve texture and flavor. For longer storage, freeze portions in airtight containers; thaw in the refrigerator overnight before warming.

Ingredient Substitutions

If you cannot find granulated vegetable bouillon, gluten free chickpea miso is a wonderful substitute added directly to marinara to provide umami and salt depth. Swap the marinara for a homemade tomato sauce simmered with sofrito and sweet paprika for a brighter, more peppery base. Gold zucchini can replace yellow squash to keep the color palette bright with a similar texture that cooks evenly.

Serving Suggestions

Enjoy the casserole alongside crusty artisan bread to mop up the luscious sauce. Serve as a side to grilled fish or steak to add a fresh, seasonal vegetable component, and top with fresh basil leaves or a sprinkle of toasted pine nuts for added texture and aroma.

Let the casserole rest before serving so the juices settle and flavors deepen. It makes a beautiful makeahead dish for gatherings.

Common Questions About Recipes

→ What vegetables are best for this dish?

Thin rounds of zucchini, yellow squash, eggplant, tomatoes, and optionally red bell pepper provide balanced texture and flavor.

→ How do I prevent watery casserole?

Lightly salting and resting sliced vegetables draws out excess moisture for a firmer, more caramelized finish.

→ Can I make it vegan and gluten-free?

Yes, use vegan marinara sauce and gluten-free vegetable bouillon or chickpea miso to keep it vegan and gluten-free.

→ Why cover the dish with parchment and foil during baking?

Covering traps steam to soften vegetables evenly, then uncovering allows edges to caramelize for added texture.

→ What is the purpose of layering vegetables upright?

Shingling the slices upright ensures even cooking, prevents steaming, and creates an attractive presentation.

→ Any tips for seasoning the marinara base?

Stir vegetable bouillon into warm marinara and taste before adding salt to balance the flavor without overpowering.