Bring a large pot of salted water to a boil. Add the pasta and cook according to package instructions until al dente. Reserve 1 cup of pasta water, then drain and set aside.
In a large skillet, heat the olive oil over medium heat. Add the chopped onion and sauté for 3-4 minutes until it becomes translucent, stirring occasionally.
Add the minced garlic and diced red bell pepper to the skillet. Cook for an additional 2-3 minutes, until the pepper softens.
Stir in the sliced mushrooms, oregano, salt, and pepper. Cook for 5-7 minutes, mixing occasionally, until the mushrooms have released their moisture and are tender.
Fold in the fresh spinach and cook until wilted, about 2 minutes.
Lower the heat and add the cream cheese to the skillet, stirring until melted and well incorporated with the vegetables. If the mixture seems too thick, gradually add some reserved pasta water until you reach the desired creaminess.
Combine the cooked pasta with the vegetable and cream cheese mixture, stirring to coat everything evenly. Mix in the grated Parmesan cheese, adjusting seasoning as necessary.
Sprinkle the stuffing crumbs over the top of the pasta, allowing them to absorb some of the sauce while adding a delightful texture. Let everything warm through for 2 minutes.
Garnish with chopped parsley before serving warm, inviting everyone to dig in.