Lightly coat a baking sheet with nonstick cooking spray.
In a large bowl combine flour, sugar, baking powder, blueberries and salt. In a separate bowl combine banana, oil, vanilla and egg. Add banana mixture to flour mixture and stir to combine. (The dough will be very sticky.)
Lightly coat work surface with flour and turn the dough out onto the floured surface. With floured hands, shape dough into 2 rolls 8 inches long and 3 inches wide. Place rolls on baking sheet. Slightly flatten rolls.
Bake 25 minutes. Remove from oven and let cool 10 minutes on baking sheet.
Transfer rolls to a cutting board. With a serrated knife, cut each roll diagonally into 12 slices 1/2-inch thick. Return slices to baking sheet.
Reduce oven temperature to 250F. Bake 15 minutes. Turn biscotti over and bake 15 minutes more.
Transfer biscotti to a wire cooling rack and let cool completely. Store in an airtight container for up to 1 week.