In a large bowl combine flour, sugar, baking powder, salt, and nutmeg. Using a pastry blender, cut in butter until mixture resembles coarse crumbs. In a small bowl beat egg and milk with a fork; add to flour mixture all at once. Mix well.
On a lightly floured surface, knead dough by folding and gently pressing dough for 10 to 12 strokes. Remove about one-third of the dough; cover and chill. Pat remaining dough into a greased 11- to 12-inch metal pizza pan. Arrange nectarine slices and blueberries evenly on dough in pizza pan. Gently spread peach preserves over fruit.
Roll chilled dough into an 11- to 12-inch circle; cut into irregular-size strips. Arrange strips over fruit in a mock-lattice pattern.
Prepare grill for indirect grilling, except omit drip pan. Test for medium heat above the center of the grill. Place pizza pan on grill rack in the center of the grill (not over heat). Cover and grill for 35 to 45 minutes or until lattice-top crust is light brown and firm.
Cool on a wire rack for 30 minutes. Serve warm. If desired, garnish with fresh herbs. Makes 8 servings.