Preheat your oven to 375°F (190°C) to create the perfect cooking environment.

In a large skillet, heat olive oil over medium heat. Add chopped onion and minced garlic, sautéing until fragrant and the onion becomes translucent, about 3-4 minutes.

Add diced zucchini and chopped bell peppers to the skillet, stirring well to combine. Cook for approximately 5-7 minutes, or until the vegetables are tender.

Pour in vegetable broth and bring the mixture to a gentle simmer. Season with salt, pepper, and Italian seasoning to taste, simmering for about 3 minutes.

Carefully transfer the vegetable mixture to a greased baking dish, spreading it evenly.

Sprinkle an even layer of shredded cheese over the top of your casserole, covering the vegetables completely.

Place the baking dish in the preheated oven and bake for 25-30 minutes until the cheese is bubbly and golden brown.

Remove the casserole from the oven and let it cool for about 5 minutes before serving.