Preheat an outdoor grill for medium-high heat and lightly oil the grate.

Grill apples and peaches until browned, about 3 minutes per side. Cut into bite-size pieces. Spread in a 9-inch oven-safe baking dish.

Mix 6 tablespoons butter, brown sugar, and cinnamon into the peaches.

Place apple crisp and cinnamon granola bars in a resealable plastic bag; crush with a heavy object. Sprinkle over mixture in the dish. Drizzle remaining 2 tablespoons butter over granola.

Transfer baking dish to the grill; cover and cook until flavors combine, 10 to 12 minutes. Allow to cool slightly before serving, 5 to 10 minutes.