Preheat the oven to 350 degrees F. Line a baking sheet with parchment. Whisk together the flour, granulated sugar, baking powder, ginger, orange zest and salt in a large bowl.
Whisk together the oil, eggs and bourbon in a small bowl and add to the dry ingredients, stirring just until combined. The dough will look crumbly at first, then sticky.
Heavily dust your work surface with confectioners' sugar and turn out the dough. Knead until smooth, then shape into a 10-by-2 1/2-inch slightly flattened log and transfer to the prepared baking sheet. Bake until golden and firm, 25 to 30 minutes. Set aside until cool enough to handle, 10 to 15 minutes. Meanwhile, reduce the oven temperature to 300 degrees F.
When the baked log is cool enough to handle, transfer to a work surface and slice with a serrated knife crosswise 1/3 to 1/2 inch thick. Lay the slices cut-side down on the same baking sheet. Bake until golden brown and firm, flipping the biscotti halfway through, about 30 minutes total. Let the biscotti cool on a wire rack before serving. Store in an airtight container for up to 10 days or freeze for up to 2 months.