Dinner

Rainbow Vegetable Gratin Recipe

ByHarper Ellington November 11, 2025November 11, 2025

Introduction

Rainbow Vegetable Gratin is a vibrant and hearty dish featuring a variety of colorful vegetables baked in a creamy sauce topped with a crispy, golden crust. This visually appealing and nutrient-packed gratin works perfectly as a side dish or a satisfying vegetarian main course. Its delightful blend of flavors and textures is sure to please your taste buds!

The image shows a rectangular white enamel baking dish filled with a layered vegetable gratin. The top layer consists of round slices of red and yellow tomatoes sprinkled with golden-brown crispy breadcrumbs and some green herbs. Beneath the tomato layer, there are visible pieces of broccoli and purple eggplant, both cooked and slightly browned. The base layer appears creamy and light, likely a cheese or sauce base, partially seen around the edges. The dish rests on a white marbled textured surface. Photo taken with an iphone --ar 4:5 --v 7

Ingredients

2 cups zucchini, sliced
2 cups bell peppers (red, yellow, green), chopped
2 cups carrots, sliced
2 cups broccoli florets
1 cup cherry tomatoes, halved
1 medium onion, chopped
3 cloves garlic, minced
2 tablespoons olive oil
Salt and pepper to taste
1 teaspoon dried thyme (or fresh thyme)
1 teaspoon dried oregano
1 cup heavy cream (or plant-based cream)
1 cup shredded cheese (cheddar, mozzarella, or a vegan alternative)
1/4 cup grated Parmesan cheese (optional)
2 tablespoons all-purpose flour
1 tablespoon Dijon mustard (optional)
1 cup breadcrumbs (panko or regular)
2 tablespoons olive oil
Fresh herbs for garnish (such as parsley or basil)

Instructions

Step 1: Preheat your oven to 375°F (190°C). Grease a large baking dish or gratin dish with olive oil or cooking spray.
Step 2: In a large skillet over medium heat, heat olive oil and sauté the chopped onion and minced garlic until translucent. Stir in zucchini, bell peppers, carrots, and broccoli. Season with salt, pepper, thyme, and oregano. Sauté for 5–7 minutes until vegetables are slightly tender. Gently fold in the cherry tomatoes and remove from heat.
Step 3: In a saucepan over medium heat, whisk together the flour and a splash of cream until smooth. Gradually add the remaining cream, stirring continuously until the mixture thickens. Remove from heat and stir in shredded cheese, Parmesan (if using), Dijon mustard, salt, and pepper until well combined and creamy.
Step 4: Spread the sautéed vegetables evenly in the prepared baking dish. Pour the creamy cheese sauce over the vegetables, ensuring they are well coated.
Step 5: In a small bowl, combine breadcrumbs, olive oil, and grated Parmesan (if using). Mix until evenly coated. Sprinkle the breadcrumb mixture evenly over the top of the gratin.
Step 6: Bake in the preheated oven for 30–35 minutes, or until the top is golden brown and the vegetables are tender. Remove from the oven and let cool slightly before serving.
Step 7: Garnish with fresh herbs if desired and serve warm as a side dish or main course.

Tips & Variations

Use any seasonal vegetables like eggplant, asparagus, or spinach to customize the gratin.
For a vegan version, substitute plant-based cream and cheese alternatives.
Add red pepper flakes or your favorite hot sauce to the creamy sauce for a spicy kick.

Storage

Store leftover gratin in an airtight container in the refrigerator for up to 3 days. Reheat in the oven or microwave until warmed through. You can also freeze the assembled gratin before baking by covering it tightly and freezing for up to 2 months. Bake from frozen, adding extra cooking time as needed.