Gather all ingredients. Preheat the oven to 350 degrees F (175 degrees C).

Bring a large pot of salted water to a boil. Cook the manicotti tubes for 2 minutes less than package directions (they should be slightly undercooked as they will continue cooking in the oven). Drain carefully and set aside on a clean kitchen towel to prevent sticking.

In a medium bowl, combine the ricotta, 1½ cups of mozzarella, ¼ cup of Parmesan, eggs, parsley, salt, pepper, and garlic powder. Mix until well combined and smooth.

Spread 1 cup of marinara sauce in the bottom of a 9x13 inch baking dish.

Using a piping bag or a small spoon, carefully fill each manicotti tube with the cheese mixture. Work gently to avoid breaking the pasta.

Arrange the filled manicotti in a single layer in the prepared baking dish.

Pour the remaining 2 cups of marinara sauce over the top of the filled manicotti, ensuring all pasta is covered.

Sprinkle with the remaining ½ cup mozzarella and ¼ cup Parmesan cheese.

Cover with aluminum foil and bake for 35 minutes. Then remove the foil and bake for an additional 10-15 minutes until the cheese is bubbly and starting to brown.

Allow to rest for 5 minutes before serving. Garnish with fresh basil if desired.