Preheat grill to medium-high heat (350° to 400°). Combine 1/8 teaspoon salt and next 7 ingredients in a large bowl, stirring gently until well blended. Pour into a buttered 10-inch cast iron skillet.
Combine flour, sugar, baking powder, and remaining 1/8 teaspoon salt in a medium bowl. Cut butter into flour mixture with a pastry blender until coarse crumbs form. Add cream, and stir just until mixture forms a soft dough. Spoon topping over berry mixture.
Grill, covered with grill lid, 25 to 30 minutes or until fruit is bubbly and topping is cooked through.