Add the ground beef, onions and mushrooms to a skillet and saute until the meat is browned and vegetables have softened. Drain the excess fat.

Reduce the heat to medium, and stir in the oregano, marinara and salt and pepper to taste. Set aside.

While the meat mixture is cooking, cook the lasagna noodles to al dente in a pot of boiling water. Rinse under cold water and drain well.

Stir together the Parmesan cheese, eggs and ricotta until well combined.

Add salt and pepper to taste.

Heat the oven to 375.

Spread a thin amount of the meat sauce into a greased 9x13 baking dish.

Top with a layer of four noodles, some of the ricotta mixture, a layer of mozzarella cheese and pepperoni slices, and then more sauce.

Repeat these layers until all of the ingredients have been used.

Bake covered with foil for 35 minutes.

Let cool for 10-15 minutes before serving.