Preheat the oven to 350 degrees F (175 degrees C). Generously grease two 8 inch square baking dishes.
Shred the potatoes and place them in a bowl of cold water to prevent discoloration. In a large bowl, beat the eggs and 2 tablespoons of oil together. Stir in the onion. Drain the potatoes, and stir them into the egg mixture as well. Gradually mix in the matzo meal and baking powder. Season with salt and pepper. Divide the mixture between the two prepared pans, and spread evenly. Drizzle or brush remaining oil over the top.
Bake for 1 hour in the preheated oven, or until nicely browned. Serve hot or cold.