Heat the oven to 350°F and line a large baking sheet with parchment. Whisk the flour, baking powder and salt in a medium bowl.
In a large bowl, whisk the sugar, eggs, oil, vanilla and orange zest until smooth. Stir in the flour mixture until just combined, then fold in the pistachios and cranberries. The dough will be sticky.
Divide the dough in half. With damp hands, shape each half into a 12 x 3-inch log on the prepared sheet, keeping 3 inches between them.
Bake 25-27 minutes, until the logs are set and lightly golden at the edges. Cool on the sheet for 15 minutes, then reduce the oven to 325°F.
Move the logs to a cutting board and slice diagonally into 1/2-inch pieces, about 12 per log. Arrange the slices cut-side down on the sheet.
Bake 9 minutes, flip each biscotto, and bake 8 minutes more, until dry and crisp at the edges.
Cool completely on a wire rack, about 15 minutes; the biscotti crisp as they cool. Store in an airtight container for up to 2 weeks.
