Preheat oven to 425°.
Roll out bottom pie crust; place in 10 inch pie pan. Reserve.
Cook, stirring continuously, carrots, celery, onion, oregano, parsley, salt & pepper, in 2 tablespoons butter.
When vegetables have softened slightly, add bouillon and water. Bring to a boil.
Add potatoes, cook until tender. Potatoes should remain firm, avoid over-cooking.
Melt 2 tablespoons butter in saucepan; stir in turkey and flour. Add milk and heat through.
Combine turkey and vegetable mixture; cook until thickened.
Fill unbaked pie crust with heated mixture. Put top crust in place, press down the edges. Slit the top crust to let out steam.
Bake for 15 minutes. Reduce temperature to 350°; bake for 20 minutes more until crust is golden brown.