01 - Preheat oven to 350°F. Grease and line a 9x9-inch baking pan with parchment paper.
02 - Whisk pumpkin puree, sugar, eggs, vegetable oil, and vanilla extract together until smooth in a large bowl.
03 - In a separate bowl, stir together flour, cinnamon, ginger, nutmeg, baking powder, baking soda, and salt.
04 - Fold dry ingredients into wet mixture until just combined, taking care not to overmix.
05 - Combine oats, pecans, brown sugar, flour, cinnamon, and salt in a medium bowl. Stir in melted butter until coarse crumbs form.
06 - Pour batter into prepared pan, smooth the surface, then evenly sprinkle the crisp topping over the top.
07 - Bake for 40 minutes until a toothpick inserted comes out clean and topping is golden and crisp.
08 - Let bars cool completely in the pan, then lift out using parchment and cut into 12 bars.