Preheat oven to 350 degrees. While the oven is preheating, cook the jumbo shells in boiling water until done. When done, drain rinse with cold water to cool them down enough to stuff them.
Mix together the cheese mixture. Add the ricotta, 2 c. of mozzarella, Parmesan cheese, and oregano.
In a separate bowl, mix together the Prego, 2 tsp of oregano, onion powder, and garlic salt. If you want you can add a pinch of sugar to take some of the tang of the spaghetti sauce away. Just taste as you go to get the sauce to your liking.
Once the shells have been cooked, stuff them with the cheese mixture. In a 9×13 baking dish, add a think layer of the pasta sauce. Just enough to cover the bottom.
Place the stuffed shells in a single layer in the baking dish. Pour the remaining sauce over the top of the shells. Sprinkle the remaining 2 c. of Mozzarella cheese on top.
Cover with foil and bake for about 35 min or until the sauce on the bottom is kind of bubbling.
Uncover and bake for another 5-10 minutes so the cheese on top browns just a tad bit.