Heat oil in a large skillet over medium heat. Add onion and garlic and cook until softened, about 5 minutes. Add tomato sauce, Italian seasoning, salt, and pepper. Simmer for 10 minutes.
Lightly grease a 9x13 inch baking dish. Spread 1/4 of the tomato sauce mixture in the bottom of the dish. Layer 1/4 of the potato slices over the sauce. Sprinkle with 1/4 of the Parmesan and mozzarella cheese. Repeat layers twice more.
Cover with remaining tomato sauce and cheese. Bake in preheated oven for 45 minutes. Sprinkle with parsley before serving.
Interesting Facts
This potato lasagna is a great way to use up leftover potatoes.
You can also add vegetables such as mushrooms, spinach, or bell peppers to the lasagna.
Leftovers can be stored in the refrigerator for up to 3 days.