Preheat the oven to 350F. Lightly grease a 9x13 baking dish.
In a large pot of boiling salted water, cook the manicotti according to the instructions until al dente. Drain in a colander and cool under cold running water. Toss with a little olive oil to prevent them from sticking together. Set aside.
1 (8-ounce) box manicotti noodles
In a mixing bowl, add the ricotta, parsley, garlic powder, egg, and parmesan. Stir with a spatula to combine. Season with salt and pepper.
1 (15-ounce) container ricotta cheese, 3 tablespoons parsley, 1 teaspoon garlic powder, 1 large egg, ½ cup parmesan cheese, Kosher salt & black pepper to taste
Add half the marinara sauce to the bottom of the prepared baking dish. Pipe the cheese mixture into each manicotti shell and place into the baking dish. Repeat with all shells. Add the remaining sauce over top of the pasta. Sprinkle the top with mozzarella.
1 (24-ounce) jar marinara sauce, 2 cups shredded mozzarella
Bake for 35 minutes or until hot throughout and the cheese is melted.