Preheat the oven to 375 degrees F and butter a 2-quart baking dish.
Make the filling: Toss the blueberries, granulated sugar, flour, lemon juice and salt in a medium bowl. Transfer to the prepared baking dish.
Make the topping: Combine the brown sugar, flour, oats, nuts, lemon zest, cinnamon and salt in a separate bowl. Using your fingers or a pastry blender, work the butter into the flour mixture until coarse crumbs form. Scatter the topping over the blueberry mixture.
Set the dish on a baking sheet and bake until the topping is golden brown and the filling is bubbling, 45 to 50 minutes. Let cool slightly before serving.