If you’re making your own balsamic reduction, pour balsamic vinegar in a small saucepan over low heat and let it simmer until it is reduced to about 2 tablespoons, about 10-15 minutes. Remove from heat and let cool.
Preheat your grill to medium high heat.
Arrange squash and peaches on a baking sheet and drizzle generously with olive oil, salt, and pepper. Place on grill and cook squash for about 2 minutes per side. Peaches will take about 3-4 minutes. Transfer back to baking sheet.
Arrange squash slices on a platter. Slice each peach half into 3-4 smaller pieces, then place on top of squash. Sprinkle mint, basil, and blue cheese on top. Drizzle balsamic reduction to finish.