In a large bowl, combine pears, white sugar, flour, cinnamon, nutmeg, cloves, salt, ginger, cardamom, and allspice. Stir until pears are evenly coated.
Pour mixture into the unbaked pie crust.
In a medium bowl, cream together butter and brown sugar. Stir in oats, walnuts, and vanilla extract. Sprinkle over the top of the pie.
Bake in the preheated oven for 40 to 50 minutes, or until crust is golden brown and filling is bubbly.
Interesting Facts
Bartlett pears were first grown in the United States in 1799.
They are the most popular variety of pear in the United States.
Bartlett pears are the only pears suitable for canning.