Preheat your oven to 350°F (175°C). Grease a 9x13 inch baking pan or line it with parchment paper for easy removal.
In a large mixing bowl, whisk together the pumpkin puree, granulated sugar, brown sugar, vegetable oil, eggs, and vanilla extract until well combined.
In another bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg, ginger, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix.
If desired, fold in the chopped nuts or chocolate chips.
Pour the batter into the prepared baking pan and spread it evenly.
Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Allow the bars to cool in the pan for about 15 minutes before transferring them to a wire rack to cool completely.
Once cooled, cut into squares and enjoy your delicious Pumpkin Bars!