Preheat the oven to 375°F (190°C).
In a skillet, heat olive oil over medium heat.
Add the minced garlic and sliced mushrooms, cooking until the mushrooms are soft.
Stir in the chopped spinach and cook until wilted.
In a bowl, combine ricotta cheese, half of the mozzarella, half of the Parmesan, oregano, salt, and pepper.
Spread a thin layer of the ricotta mixture on the bottom of a baking dish.
Layer three lasagna noodles over the ricotta mixture.
Spoon half of the mushroom and spinach mixture over the noodles.
Add half of the remaining ricotta mixture, spreading it evenly.
Repeat the layers: noodles, vegetable mixture, and ricotta, until all ingredients are used.
Finish with a final layer of noodles and top with remaining mozzarella and Parmesan.
Cover the dish with aluminum foil and bake for 25 minutes.
Remove the foil and bake for an additional 15 minutes.
Let it cool for 10 minutes before slicing.