Preheat your oven to 350°F (175°C).
In a large mixing bowl, whisk together the dry ingredients: flour, baking powder, baking soda, cinnamon, nutmeg, ginger, and salt.
In another bowl, mix the wet ingredients: granulated sugar, brown sugar, pumpkin puree, vegetable oil, eggs, and vanilla extract. Stir until smooth.
Gradually add the dry ingredients to the wet mixture, stirring gently until just combined.
In a medium bowl, prepare the crumble topping by mixing flour, oats, brown sugar, and cinnamon. Stir in melted butter until crumbly.
Pour the cake batter into a greased 9x13 inch baking pan and spread evenly. Sprinkle the crumble topping over the batter.
Bake for 30-35 minutes, checking for doneness with a toothpick.
Allow the cake to cool in the pan for at least 15 minutes before slicing and serving.