In a medium bowl, toss together 3 nectarines (quartered and pitted) with 2 tablespoons sugar; set aside to macerate. About 15 minutes.
Heat grill to medium. Stack 2 pieces of foil; place on grill. With a slotted spoon, transfer nectarines to foil; reserve any juice that has accumulated in bowl. Cover grill and cook until nectarines are charred and softened, turning occasionally, 10 to 15 minutes.
Return nectarines to bowl; add ½ pint blueberries, and toss to combine. Divide fruit evenly among four serving bowls; drizzle reserved juice over the top. Serve with a scoop of ice cream.