Preheat the oven to 375°F. Lightly spray a 9 x 13-inch baking dish with nonstick cooking spray.

Spread a thin layer of the 25‑ounce jar of sauce (about 1/4 to 1/3 cup) on the bottom of the prepared dish.

Arrange a single layer of ravioli from the 25‑ounce package over the sauce so the ravioli cover the bottom of the dish.

Spoon about 1 cup of sauce evenly over the ravioli, then sprinkle 1 cup of the 3 cups shredded mozzarella evenly over the sauce.

If ravioli remain, add another single layer of ravioli, then spoon about 1 cup more sauce over them and sprinkle with the second 1‑cup portion of mozzarella.

If there is a final layer of ravioli, place it in the dish, spread the remaining sauce from the jar over the top, and sprinkle the remaining 1 cup of mozzarella evenly over everything.

Sprinkle the 3 tablespoons of shredded parmesan cheese evenly over the top layer of mozzarella.

Cover the baking dish tightly with aluminum foil and bake in the preheated oven for 25 minutes (bake 30 minutes if using frozen ravioli).

Carefully remove the foil and return the dish to the oven. Bake uncovered 5–7 minutes more, until the cheese is melted and bubbly and the top is lightly browned.

Remove from the oven, let rest a few minutes, then sprinkle with chopped parsley before serving.