Preheat the oven to 350°F (180°C) and line two large cookie sheets with parchment paper.
Sift all purpose flour into a mixing bowl and add rolled oats, dessicated coconut, baking soda, salt and pumpkin pie spice. Mix together.
Add butter and light brown sugar to the bowl of your stand mixer (or you can use a large bowl with a handheld mixer) and beat until well combined.
Add pumpkin purée and vanilla extract and beat in until well mixed.
Add dry ingredients to wet and mix in with a spoon or spatula into a thick cookie dough.
Break off pieces of the dough and roll into balls and place them onto parchment lined cookie sheets. Aim to get 20 cookies in total spread over two large cookie sheets (10 per sheet).
Bake one tray at a time for 15 minutes. If they are puffy when they come out of the oven, then press down gently with a fork to flatten.
Let them cool and firm up directly on the tray. When they are completely cooled, prepare the frosting.
Sift powdered sugar into a bowl. Add soy milk and vanilla extract and mix it into a thick frosting.
Use a teaspoon to spoon the frosting on top of the cookies. Place the cookies into the fridge for 10 minutes for the frosting to set.
And your cookies are ready to serve!