Preheat your outdoor grill or grill pan to medium-high.
Coat chicken breasts with olive oil, balsamic vinegar, garlic powder, Italian seasoning, and salt and pepper. Grill chicken for about 15 minutes, flipping halfway through cooking time. Top chicken with 2 slices mozzarella each, cover grill, and allow chicken to cook through, about 5 minutes more.
In a medium bowl, combine tomatoes and minced garlic. Add a splash of olive oil and balsamic vinegar. Season with salt and pepper; toss to coat. Serve chicken, spoon tomato mixture over each portion, and sprinkle with fresh basil.
Enjoy! (This is great served with crusty bread and a salad!)