Bring 1 cup water and oats to a boil in a saucepan; reduce heat and simmer until water is absorbed, 10 minutes. Bring 1 1/2 cups water and millet to a boil in a separate saucepan; reduce heat and simmer until water is absorbed and millet is tender, 20 minutes.

Preheat oven to 350 degrees F (175 degrees C).

Combine oats, millet, onion, carrot, celery, potato, safflower oil, tamari, allspice, nutmeg, cloves, salt, and black pepper together in a large bowl; mix well.

Press 1 pie crust pastry into a 9-inch pie pan. Pour filling into pie crust. Top with second pie crust pastry; pinch edges together. Pierce a few areas of the top crust to allow pie to ventilate during baking. Brush top crust with beaten egg.

Bake pie in the preheated oven until crust is golden brown, about 40 minutes.