Preheat the oven to 350°F. Line a 9x13 with parchment paper or foil sprayed with cooking spray, set aside. In a medium-sized bowl stir together the flour, pumpkin spice, and salt until combined.

In a large bowl cream together the butter and brown sugar until smooth, 2 minutes. Add the dry ingredients and mix it in until just combined with no dry patches. Press this into the bottom of the baking dish. Bake for 20 minutes.

While the crust is baking make the filling. In a large bowl whisk together the pumpkin mix, eggs, and evaporated milk until smooth. Pour this over the crust.

In a large bowl stir together the brown sugar, flour, oats, pumpkin spice, and salt. Add the butter and cut it in with a pastry cutter or use your finger to combine the mixture to resemble wet sand.

Sprinkle the streusel over the pumpkin filling. Bake for 60-70 minutes until the crust is lightly golden brown. Place it on a wire rack to cool completely. Place it in the fridge for at least 4 hours to set, even best overnight. Cut into bars.

In a small bowl, whisk together the powdered sugar, milk, and vanilla until smooth. Drizzle the glaze over the bars, let sit for 10 minutes and serve.