Preheat oven to 350Âº.
Combine the flour, sugar, baking powder, and salt.
Combine banana, oil, vanilla. Stir in flour mixture and pecans (dough will be sticky).
Shape dough into a flattened log with floured hands. It is much easier to form this on a baking sheet coated with cooking spray. Flatten to 1/2-inch thickness.
Bake at 350Âº for 25 minutes.
Remove rolls from baking sheet. Cool 10 minutes on a wire rack.
Cut the log diagonally into 12 (1/2-inch) slices.
Place slices, cut sides down, on baking sheet.
Reduce oven temperature to 250Âº.
Bake 15 minutes. Turn cookies over. Bake an additional 15 minutes. Remove from baking sheet. Cool completely on wire racks.