Preheat your oven to 375°F (190°C).
Fit the pie crust into a 9-inch pie pan and set aside.
In a large bowl, combine the cranberries, granulated sugar, 1/4 cup of flour, and salt. Mix well and pour into the prepared pie crust.
In another bowl, make the streusel topping by mixing together the remaining 1/4 cup of flour, rolled oats, brown sugar, and cold cubed butter. Use your hands or a pastry cutter to crumble the mixture until it resembles coarse breadcrumbs.
Sprinkle the streusel topping evenly over the cranberry mixture in the pie crust.
Bake in the preheated oven for about 45 minutes, or until the topping is golden brown and the cranberries are bubbly.
Allow the pie to cool before serving, letting it set for at least 15 minutes. Serve warm or at room temperature.