Preheat the oven to 350 °F . Line 2 baking sheets with parchment paper.
With an electric mixer, cream together the room-temperature butter, granulated sugar and brown sugar for about 2 minutes, until the butter is light and fluffy.
Beat in the egg
Beat in the vanilla extract and canned pumpkin.
In a separate bowl, whisk together the all-purpose flour, the baking powder and the spices.
Add the flour mixture to the pumpkin mixture and stir together until completely blended.
Stir in the oats
Stir in the cranberries
Drop teaspoonfulls of the cookie dough onto the prepared baking sheets. You'll end up with 12 cookie dough balls per sheet.
Pop each baking sheet in the oven, one at a time. Bake for about 10 minutes (I found that it took about 12 minutes for my cookies to bake, but cookies tend to cook really fast, and it's really easy to go from "not quite done" to "absolutely torched". Keep an close eye on them after the 10-minute mark.)