In a bowl, combine oats, flour, brown sugar, ginger, and salt. Pour in melted butter and stir until it forms clumps.
Set aside 1/2 cup of the crumbles and press the rest into an even layer in bottom of a pan. Press firmly.
Scatter half of the berries over the layer. Sprinkle cornstarch, lemon juice, and 1/2 tbsp of granulated sugar on top. Scatter on remaining berries, remaining 1/2 tbsp of sugar, then the reserved crumbles.
Bake for 35-40 minutes, Cool completely before serving.