Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the pumpkin puree, brown sugar, vanilla extract, cinnamon, nutmeg, salt, and eggs. Mix well until the ingredients are fully combined and smooth.
Pour the pumpkin mixture into a greased 9x13 inch baking dish, spreading it evenly across the bottom.
In another bowl, combine the rolled oats, flour, melted butter, chopped nuts, and granulated sugar. Mix until everything is well coated and crumbly.
Sprinkle the oat mixture evenly over the top of the pumpkin layer.
Bake in the preheated oven for 45 minutes, or until the topping is golden brown and the pumpkin filling is set.
Remove from the oven and allow it to cool slightly before serving.
Serve warm or at room temperature, with whipped cream or ice cream for an extra treat.