Prepare quinoa according to package directions.
Preheat oven to 375 F.
In large skillet, heat oil over medium heat. Add garlic and onions; saute 1 minute. Add mushrooms and cook 5 minutes, stirring occasionally. Add spinach and stir until wilted, about 2 minutes. Stir in tomato sauce and keep warm.
In medium bowl, combine ricotta, egg, 1/4 cup Parmesan cheese and Italian seasoning.
Place 1 cup sauce in bottom of 2-quart baking dish. Spread half of quinoa evenly over sauce. Top with half of ricotta mixture. Top with 1 cup sauce. Sprinkle with 1 cup mozzarella. Repeat layers, finishing with remaining mozzarella and Parmesan cheese.
Bake uncovered 30 minutes. Serve warm.