1. Heat a grill pan over medium heat. Add peaches and grill until outsides are caramelized.
2. Meanwhile, preheat oven to 350 degrees Fahrenheit. Combine balsamic vinegar and brown sugar in a small saucepan over medium-low heat. Let simmer until vinegar reduces and mixture is thick and syrupy.
3. Transfer peaches to a lined baking sheet. Brush with balsamic glaze and bake for 15 minutes.