In a large skillet, heat the olive oil over medium heat. Add the diced onion and sauté until translucent, about 3-4 minutes.
Add the minced garlic and ground beef to the skillet. Cook until the beef is browned, breaking it apart with a spoon, about 5-7 minutes. Drain excess fat if necessary.
Stir in the diced tomatoes (with juice), beef broth, Italian seasoning, salt, and pepper. Bring the mixture to a simmer.
Add the orzo pasta to the skillet, stirring to combine. Cover and cook for about 10-12 minutes, or until the orzo is tender and has absorbed most of the liquid, stirring occasionally.
Once the orzo is cooked, remove the skillet from heat. Sprinkle the shredded mozzarella cheese on top and cover for a few minutes until the cheese is melted.
Garnish with chopped parsley before serving.