1. Preheat oven to 375°F (190°C).
2. Cook lasagna noodles according to package instructions. Drain and set aside.
3. In a saucepan, heat olive oil over medium heat. Add chopped onion and minced garlic, sauté until translucent.
4. Add ground beef to the saucepan, cook until browned. Drain excess fat.
5. Stir in marinara sauce, salt, pepper, and dried oregano. Simmer for 10 minutes.
6. In a mixing bowl, combine ricotta cheese and 1 cup of mozzarella cheese.
7. In a baking dish, spread a thin layer of meat sauce. Layer with lasagna noodles, ricotta mixture, and meat sauce. Repeat layers, ending with meat sauce.
8. Top with remaining mozzarella cheese and Parmesan cheese.
9. Cover with aluminum foil and bake for 25 minutes. Remove foil and bake for an additional 25 minutes, or until cheese is golden and bubbly.
10. Let lasagna rest for 10 minutes before serving.