Preheat an oven to 350 degrees F. Grease a 9x13 inch pan with 1 tablespoon of vegetable oil.
Combine the potatoes and onions in a large bowl. Mix in the eggs, 1/3 cup of vegetable oil, salt, and pepper. Pour the mixture into the prepared pan.
Bake in the preheated oven until the top is golden brown and crisp, 1 1/2 to 2 hours.