Preheat the grill to medium heat, ensuring the grates are clean and lightly coated with olive oil.

In a mixing bowl, toss zucchini, red bell pepper, and red onion with olive oil, salt, pepper, oregano, and basil.

Spread the seasoned vegetables evenly on the grill and grill for 5-7 minutes, turning occasionally.

Sauté minced garlic in olive oil for 30 seconds, then add spinach and cook until wilted, about 1-2 minutes.

Assemble the quesadillas by layering grilled vegetables, sautéed spinach, cherry tomatoes, feta, and mozzarella on half of each tortilla.

Grill each quesadilla for 3-4 minutes per side until golden brown and cheese is melted.

Let the quesadillas rest for 5 minutes, then cut into wedges and serve warm.