Grate potatoes and onions. Mix in eggs, oil, and boiling water. Season with salt and pepper.
Transfer the potato mixture to a 9x13 inch pan. Bake uncovered for 2 hours.
After 2 hours, cover very tightly with 3 layers of foil. Place a 9x13 pan filled halfway with cold water on the bottom rack of the oven. Place the covered kugel on the oven rack directly above the water. Lower oven temperature to 220°F and bake for 8 hours or overnight.