Preheat the oven to 350°F. Line 2 sheet pans with parchment paper.
In a medium mixing bowl, combine the flour, oats, pumpkin pie spice, baking powder, baking soda, and salt.
Cream the butter, granulated sugar, and brown sugar in the mixer until light and fluffy, about 2 to 3 minutes.
Mix in the pumpkin purée, egg, and vanilla extract.
Slowly add the flour mixture to the butter mixture and mix just until combined.
Stir in the white chocolate chips.
Place the cookie dough in the refrigerator for at least 30 minutes to chill.
Scoop heaping tablespoons of dough onto the prepared sheet pans, arranging the cookies about 2 inches apart.
Bake for 12 to 14 minutes, or until the edges are golden brown.
Allow the cookies to cool on the sheet pan for 5 to 10 minutes before transferring them to a cooling rack to cool completely.