In a large pot or Dutch oven, heat the olive oil over medium heat. Add the diced onion and cook until softened, about 3-4 minutes. Stir in the minced garlic and cook for an additional minute until fragrant.

Add the ground beef to the pot, breaking it apart with a spoon. Cook until browned and no longer pink, about 5-7 minutes. Drain any excess fat if necessary.

Stir in the orzo, diced tomatoes (with their juice), beef broth, oregano, basil, salt, and pepper. Bring the mixture to a boil.

Reduce the heat to low, cover the pot, and let it simmer for about 10-12 minutes, or until the orzo is tender and most of the liquid is absorbed. Stir occasionally to prevent sticking.

Once cooked, remove the pot from heat and sprinkle the shredded mozzarella cheese on top. Cover the pot again for a few minutes until the cheese melts.

Garnish with chopped parsley before serving.