Heat one side of grill to medium-high (350 to 400 degrees).
To prepare peaches: Place peaches in a large bowl. In a small bowl, stir together 3/4 cup sugar, 2 tablespoons flour, cinnamon, salt and nutmeg. Sprinkle mixture over peaches and stir gently to combine. Spoon peach mixture into a buttered 10-inch cast-iron skillet. Cut 2 tablespoons butter into small pieces over peaches. Cover skillet tightly with aluminum foil. Place skillet over lit side of grill and grill, covered, until bubbling and hot, about 15 minutes.
To prepare biscuit topping: Stir together 1 cup flour, 1/4 cup sugar and baking powder in a small bowl. Make a well in the center and add cream and melted butter. Stir just until mixture comes together.
Uncover grill and discard foil; dollop peaches with dough mixture. Cover with grill lid and grill until biscuits are browned, about 15 minutes more. Remove skillet from grill and let stand 10 minutes before serving.