In a large sauté pan, heat olive oil over medium-high heat. Add onions and mushrooms and cook until they soften, about 5 minutes.
Add red and yellow peppers. Cook until soft, about 10 minutes.
Add spinach and season with 1/2 teaspoon each salt, pepper, and red pepper flakes. Cook until wilted, about 2 more minutes.
Set the vegetable mixture aside.
In another bowl, mix together ricotta cheese, parmesan cheese, egg, garlic, oregano, basil and remaining salt, pepper, and red pepper flakes. Set aside.
To assemble the lasagna, start by spreading a thin layer of sauce on the bottom of a 9×13 pan. Add a layer of lasagna noodles and ricotta mixture.
Add a layer of vegetables.
Add slices of fresh mozzarella and shredded mozzarella.
Repeat until you have used all of the ingredients. Top with chopped parsley.
Bake in a preheated 350 degree oven for 1 hour covered with foil. Remove the foil and bake an additional 20 minutes. Let rest for 20 minutes before slicing.