Prepare spaghetti according to package directions.
Heat oven to 375 degrees. Sauté ground beef, onion, mushrooms, garlic, oregano, salt and pepper in a large skillet until meat is browned; pour off fat. Stir in spaghetti sauce; simmer uncovered for 10 minutes.
Place half the cooked spaghetti in the bottom of a deep 8-inch square casserole dish that has been sprayed with cooking spray. Layer half the meat sauce mixture on top of spaghetti.
Combine the sour cream and cottage cheese; spread over meat sauce layer. Add remaining spaghetti and cover with remaining meat mixture. Sprinkle with Parmesan cheese. Bake for 35 minutes; let stand for 5 minutes before serving.