Preheat your oven to 350°F (175°C). Grease a 9x13 inch baking dish or line it with parchment paper for easier removal.
In a mixing bowl, combine the flour, brown sugar, oats, melted butter, cinnamon, and salt. Mix until crumbly.
Press two-thirds of the crumb mixture into the bottom of the prepared baking dish to form a crust.
In another bowl, whisk together pumpkin puree, sweetened condensed milk, eggs, vanilla, pumpkin pie spice, and salt until well combined.
Pour the pumpkin filling over the crust in the baking dish and smooth it out evenly.
Sprinkle the remaining crumb mixture over the pumpkin filling.
Bake in the preheated oven for 35-40 minutes, or until the filling is set and the topping is golden brown.
Remove from the oven and let it cool in the pan for about 15 minutes. Then transfer to a wire rack to cool completely.
Cut into bars and serve. Enjoy!