Preheat the oven to 400°F (200°C).
In a large mixing bowl, combine olive oil, Italian seasoning, salt, black pepper, and minced garlic. Mix well.
Add the chicken breasts to the bowl, coating them evenly with the marinade. Let them sit for about 10 minutes to absorb the flavors.
While the chicken is marinating, prepare the vegetables. In another bowl, combine the cherry tomatoes, bell peppers, zucchini, and red onion. Drizzle with a little olive oil and season with salt and pepper.
Once the chicken has marinated, arrange the chicken breasts in the center of the sheet pan.
Spread the prepared vegetables around the chicken on the same sheet pan.
Bake in the preheated oven for 25-30 minutes, or until the chicken is cooked through (internal temperature should reach 165°F or 75°C) and the vegetables are tender.
If desired, broil for an additional 2-3 minutes at the end to achieve a golden-brown finish on the chicken and vegetables.
Remove the sheet pan from the oven and let it rest for a few minutes. Garnish with fresh basil or parsley if desired before serving.