Begin by chopping the cauliflower, zucchini, bell peppers, and onion into bite-sized pieces. In a large skillet, heat a splash of olive oil over medium heat. Add the chopped veggies and sauté for about 5–7 minutes until they're softened and aromatic, stirring occasionally to prevent sticking.

In a spacious mixing bowl, combine the sautéed vegetables with fresh spinach, shredded cheddar cheese, and eggs. Season the mixture generously with salt, pepper, and Italian seasoning to taste.

Grease a 9x13-inch baking dish with a little olive oil or cooking spray to prevent sticking. Carefully pour the vegetable and cheese mixture into the dish, spreading it evenly across the bottom.

Preheat your oven to 375°F (190°C). Once heated, place the casserole in the oven and bake for 30–35 minutes.

After baking, remove the casserole from the oven and let it cool for about 10 minutes. Once slightly cooled, use a sharp knife to cut your portions. Serve warm.