In a large bowl beat butter with an electric mixer on medium to high speed for 30 seconds. Add granulated sugar, baking powder, and salt. Beat until combined, scraping bowl occasionally. Beat in egg until combined. Beat in as much of the flour as you can with the mixer. Stir in any remaining flour, crystallized ginger, and orange peel (mixture will be crumbly). Use your hands to knead the mixture until it comes together.
Divide dough into three portions. Shape each portion into about a 7-inch roll. Spread decorating sugar on waxed paper. Roll rolls in decorating sugar to coat. Wrap rolls in plastic wrap or waxed paper. Chill about 4 hours or until dough is firm enough to slice.
Preheat oven to 350°F. Lightly grease cookie sheets. Cut rolls into 1/4-inch slices. Place slices 1 inch apart on prepared cookie sheets. Sprinkle each slice with some of the remaining decorating sugar.
Bake for 8 to 10 minutes or until bottoms are lightly browned. Transfer to a wire racks; cool.
Layer cookies between sheets of waxed paper in an airtight container; cover. Store at room temperature for up to 3 days or freeze for up to 3 months.