Preheat the oven to 375°F (190°C).
Heat olive oil in an oven-safe skillet or baking dish and sauté the garlic, onion, and bell pepper until softened.
Add the chicken pieces and cook until lightly browned on the outside.
Stir in the orzo, diced tomatoes, chicken broth, oregano, basil, salt, and pepper.
Cover and bake for 25-30 minutes, until the orzo is tender and the chicken is cooked through.
Sprinkle with Parmesan cheese, if using, before serving.