Place blueberries in a large bowl. Combine the sugar, cornstarch, flour, cinnamon, lemon zest and juice, nutmeg and salt; sprinkle over blueberries and toss to coat. Transfer to a greased 8-in. square baking dish.
For topping, in a small bowl, combine the wafer crumbs, flour, brown sugar and cinnamon. Stir in butter until blended. Sprinkle over blueberry mixture.
Bake at 350° for 40-50 minutes or until filling is bubbly and topping is golden brown. Serve warm. Garnish with whipped cream and lemon zest if desired.