Oven-Baked Ratatouille Casserole with Herbs

Why You’ll Love This Recipe

• Classic Provençal flavors in an easy, oven-baked casserole that feels special but is weeknight-friendly.
• Light, olive-and-herb sauce lets the vegetables roast sweet and tender without getting watery.
• Beautiful layered presentation with minimal fuss—great for bringing to the table.
• Naturally vegan and gluten-free, with optional add-ins to make it heartier.

Grocery List

• Produce: Eggplant, zucchini, Roma tomatoes, red bell pepper, yellow bell pepper, yellow onion, garlic, fresh basil, fresh thyme (or use dried), lemon
• Dairy: None (optional: goat cheese or Parmesan for variations)
• Pantry: Extra-virgin olive oil, tomato paste, low-sodium vegetable broth, balsamic vinegar, dried oregano, red pepper flakes (optional), kosher salt, black pepper

Full Ingredients

Vegetables

• 1 large eggplant (about 1 lb / 450 g), sliced into 1/4 in (6 mm) rounds
• 2 medium zucchini (about 1 lb / 450 g), sliced into 1/4 in (6 mm) rounds
• 4 medium Roma tomatoes (about 1 lb / 450 g), sliced into 1/4 in (6 mm) rounds
• 2 bell peppers (1 red, 1 yellow), cored and cut into thin strips
• 1 tbsp extra-virgin olive oil, for brushing the baking dish
• 1 tsp kosher salt, for seasoning the layers
• 1/2 tsp freshly ground black pepper

Light Olive & Herb Sauce

• 1/4 cup extra-virgin olive oil (60 ml)
• 1 medium yellow onion, finely diced
• 4 garlic cloves, minced
• 2 tbsp tomato paste (35 g)
• 1/2 cup low-sodium vegetable broth (120 ml)
• 1 tbsp balsamic vinegar (15 ml)
• 2 tsp fresh thyme leaves, chopped (or 1 tsp dried thyme)
• 1 tsp dried oregano
• 1/4 tsp red pepper flakes (optional)
• 1/2 tsp kosher salt (or to taste)
• 1/4 tsp freshly ground black pepper
• 2 tbsp fresh basil, chopped

To Finish

• 1 tbsp extra-virgin olive oil, for drizzling
• 2 tbsp fresh basil, torn or chopped
• 1 tsp finely grated lemon zest

Step-by-Step Instructions

Step 1: Preheat and prepare the baking dish

Heat the oven to 400°F (200°C) with a rack in the center. Lightly brush a 9×13-inch (23×33 cm) baking dish with 1 tablespoon olive oil to prevent sticking.

Step 2: Make the light olive-herb sauce

Warm 1/4 cup olive oil in a medium saucepan over medium heat. Add the diced onion and cook, stirring, until translucent and sweet, about 5 minutes. Stir in the garlic and cook 30 seconds until fragrant. Add the tomato paste and cook, stirring, for 1 minute to caramelize its sugars.

Whisk in the vegetable broth and balsamic vinegar, then add thyme, oregano, and red pepper flakes (if using). Simmer 3 to 4 minutes until slightly thickened and glossy. Season with 1/2 teaspoon kosher salt and 1/4 teaspoon black pepper. Off the heat, stir in 2 tablespoons chopped basil. Taste and adjust seasoning; the sauce should be savory and bright.

Step 3: Slice and season the vegetables

Slice the eggplant, zucchini, and tomatoes into even 1/4-inch (6 mm) rounds. Cut bell peppers into thin strips. Optional but recommended: sprinkle the eggplant slices lightly with kosher salt and let sit in a colander for 20 minutes to draw out excess moisture and any bitterness; pat very dry with paper towels.

Step 4: Start the layer

Spread about 1/3 cup of the sauce in the bottom of the prepared baking dish. Arrange the vegetable rounds in slightly overlapping rows or a shingled pattern: alternate zucchini, eggplant, and tomato slices to create colorful stripes. Tuck bell pepper strips here and there between the slices so each row gets a little pop of sweetness and color.

Step 5: Season and sauce the top

Brush the top lightly with 1 tablespoon olive oil. Sprinkle with 1 teaspoon kosher salt and 1/2 teaspoon black pepper. Spoon the remaining sauce evenly over the vegetables, letting it seep into the cracks without drowning the layers.

Step 6: Bake covered, then uncover to finish

Cover the dish tightly with foil and bake for 30 minutes. Remove the foil and continue baking for 15 minutes, until the vegetables are very tender and the juices are bubbling. For lightly caramelized edges, broil 1 to 2 minutes, watching closely to prevent burning.

Step 7: Rest, garnish, and serve

Let the casserole rest 10 minutes so the juices settle. Finish with the remaining basil and the lemon zest. Taste and adjust salt if needed. Serve warm as a side or a light main with crusty bread or a green salad.

Pro Tips

• Uniform slices are key to even cooking; use a mandoline set to 1/4 inch (6 mm) if you have one.
• Salting and drying the eggplant prevents a watery casserole and concentrates flavor.
• Do not over-sauce; a thin layer under and a spooned drizzle on top keeps the dish light and sweet.
• Bake covered first to steam-tender the vegetables, then uncover to concentrate juices and caramelize edges.
• Let it rest before serving—10 minutes helps the layers set for cleaner slices.

Variations

• Cheesy finish: Crumble 3 oz (85 g) goat cheese or sprinkle 1/3 cup freshly grated Parmesan over the top for the last 10 minutes of baking.
• Smoky-spiced: Add 1 tsp smoked paprika and 1 tbsp harissa to the sauce in Step 2 for deeper, smoky heat.
• Hearty veggie main: Scatter 1 can (15 oz / 425 g) rinsed white beans or chickpeas between the layers before saucing.

Storage & Make-Ahead

Refrigerate leftovers in an airtight container for up to 4 days. Reheat, covered, at 350°F (175°C) for 15–20 minutes, or microwave gently until warmed through. The sauce can be made up to 4 days ahead and refrigerated; slice vegetables up to 1 day ahead and keep covered and chilled. While you can freeze baked ratatouille for up to 2 months, the vegetables will soften further upon thawing; reheat from thawed at 350°F (175°C) until hot.

Nutrition (per serving)

Approximate for 1 of 6 servings: 200 calories; 14 g fat; 19 g carbohydrates; 5 g fiber; 11 g sugars; 4 g protein; 380 mg sodium.