Pre-heat oven to 350 degrees. Grease 9×13-inch casserole dish.
Cook pasta according to package directions. Mix cooked pasta with pasta sauce and transfer into casserole dish.
Meanwhile, cook sausage. Heat a skillet over medium heat. Add sausage links and cook for 5 minutes on each side. Pour ½ cup of water into pan and immediately cover, allowing sausages to steam until fully cooked. Remove from heat and let sausages rest for 10 minutes before slicing into rounds.
Top pasta with cheese, sausage, peppers and onions. Drizzle top with olive oil and season with a few pinches of oregano.