• Arrange racks in upper and lower thirds of oven; preheat to 350°. Line 2 large baking sheets with parchment paper.
• In a large bowl, whisk flour, pumpkin pie spice, baking soda, and salt. In another large bowl, using an electric mixer on medium speed, beat butter and brown sugar until light and fluffy, about 2 minutes. Add egg, pumpkin, and maple syrup and beat on medium speed until combined, then gradually add flour mixture and beat until fully combined. Stir in oats and pecans. Cover and refrigerate until cold, about 30 minutes.
• Scoop out 16 (1/4-cup) balls of dough and arrange 2" apart on prepared baking sheets. Slightly flatten with the palm of your hand. Bake until cookies are firm and lightly browned, 14 to 16 minutes. Let cool completely.

GLAZE

• In a small bowl, whisk powdered sugar, maple syrup, and pumpkin pie spice. Add water, 1 teaspoon at a time, until icing is thick but pourable.
• Drizzle icing over cooled cookies. Let stand until icing sets, about 15 minutes.