Cook the Beef:
Preheat your oven to 375°F (190°C). In a large skillet, heat a bit of oil over medium heat. Sauté the onion until translucent, then add the garlic and sauté until fragrant. Add the ground beef and cook until browned, breaking it apart with a spoon. Drain excess fat. Stir in 1 cup of the marinara sauce, oregano, basil, salt, and pepper. Simmer for 5 minutes, then let it cool slightly.

Prepare the Filling:
In a large bowl, combine the cooked beef mixture with ricotta cheese and half of the mozzarella.

Stuff the Cannelloni:
Carefully fill each cannelloni shell with the beef and ricotta mixture using a spoon or piping bag.

Assemble the Dish:
Spread 1/2 cup of marinara sauce on the bottom of a baking dish. Arrange the filled cannelloni in a single layer over the sauce. Pour the remaining marinara sauce over the top.

Add Cheese:
Sprinkle the remaining mozzarella and Parmesan over the top.

Bake:
Cover the dish with foil and bake in the preheated oven for 20 minutes. Remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and golden.

Garnish and Serve:
Remove from the oven and let it cool slightly. Garnish with chopped parsley before serving.