Preheat the oven to 400°. Bring a medium saucepan of water to a boil. In a medium bowl, combine 1/4 cup of the brown sugar with the flour, oats, cinnamon and salt. Using your fingers or a pastry blender, work in the butter until the mixture resembles peas. Stir in the pecans.
Using a small sharp knife, make a shallow X in the bottom of each peach. Add the peaches to the boiling water and blanch for about 30 seconds, then remove and refresh with cold water. Peel, pit and slice the peaches.
In a large bowl, toss the peaches with the lemon juice, cornstarch, ginger and the remaining 2 tablespoons of brown sugar. Fold in half of the berries and spoon the fruit into a 1-quart baking dish. Sprinkle the crumbs over the fruit, top with the remaining berries and bake for about 30 minutes, or until bubbling and the top is golden.
The crumble can be baked up to 6 hours ahead and reheated before serving.