2. Heat 2 tablespoons of the olive oil in a large, heavy nonstick skillet over medium heat. Add the onion and cook, stirring often, until translucent, about 5 minutes. Add the garlic, stir together for about 30 seconds, until it begins to smell fragrant, and stir in the squash. Cook, stirring often, until the squash is translucent but not mushy, 5 to 10 minutes. Season generously with salt and pepper. Stir in the thyme and rice, and remove from the heat.
3. Beat the eggs in a large bowl. Beat in 1/2 teaspoon salt and the cheese. Stir in the zucchini mixture and combine well. Scrape into the gratin dish. Sprinkle the breadcrumbs over the top. Drizzle on the remaining tablespoon of olive oil. Bake 40 to 45 minutes, or until the top is browned and the gratin is sizzling. Remove from the heat and allow to sit for at least 10 minutes before serving. Serve hot, warm or at room temperature.
Martha Rose Schulman is a chef, cookbook author, educator and food consultant. Her cookbooks have been nominated for James Beard and IACP awards, and her series, "Recipes for Health," appears online for The New York Times.