Bring a large pot of salted water to a boil and add lasagna noodles. Cook noodles according to box’s instructions. Drain and rinse with cold water.
In a 13x9 baking dish, put 2 tablespoons of pasta sauce on the bottom and spread out to cover.
Place 3 lasagna noodles down, spread 1/5 of the pasta sauce on top of the noodles, put 1/5 of the ricotta cheese down (in dollops), add 1/5 of sliced mozzarella cheese, add 1/5 of the mushrooms. Add a sprinkle of dried oregano to season the entire layer.
Repeat noodles, pasta sauce, ricotta cheese, mozzarella cheese, mushrooms and oregano 4 more times, so you'll have a total of 5 layers.
Cover lasagna with aluminum foil and bake 30 minutes.
Remove foil and bake for 15 more minutes. Allow to cool for 5 minutes before cutting into slices.