Preheat your oven to 350°F (175°C) and prepare an 8×8-inch baking dish by lining it with parchment paper.

In a large mixing bowl, whisk together the pumpkin puree, maple syrup, nut butter, and the egg (or flax egg) along with vanilla extract until smooth.

Add the rolled oats, baking powder, pumpkin pie spice, and salt to the wet mixture. Stir until thoroughly combined.

Fold in your choice of optional mix-ins such as chocolate chips, chopped nuts, or dried fruit.

Pour the batter into the prepared baking dish and bake for 28-32 minutes, or until golden and a toothpick comes out mostly clean.

Let the bars cool completely in the pan before lifting them out and slicing into 12 bars.