Fill stock pot with water. Bring water to a boil. Add pasta and bring back to full boil. Boil pasta for 7-10 minutes or until al dente stage is reached. Drain pasta.
While noodles are boiling, brown ground beef in a frying pan. Drain excess grease.
Stir pasta sauce and oregano into cooked ground beef. Add cooked pasta and stir.
Pour mostaccioli into a casserole. Sprinkle mozarella cheese. Cover with lid and refrigerate. Bake covered at 350 degrees for 20 minutes then remove lid and finish baking uncovered for an additional 15 - 20 minutes.
If you want, you can leave out the ground beef. Also, you can add onion to this recipe for a little extra flavor :)