Heat olive oil in a large skillet over medium heat.
Add the chopped onion and cook for 3-4 minutes until softened.
Add minced garlic and cook for 1 minute until fragrant.
Add the ground beef to the skillet and cook, breaking it apart with a spoon, until browned and cooked through, about 6-8 minutes.
Drain any excess fat from the skillet.
Stir in the orzo pasta, diced tomatoes, dried oregano, dried basil, salt, and black pepper.
Pour in the beef broth and water, and bring the mixture to a boil.
Reduce heat to low, cover, and simmer for 12-15 minutes, or until the orzo is tender and most of the liquid is absorbed.
Stir in the chopped spinach and cook for an additional 2 minutes until wilted.
Remove from heat and stir in the shredded Parmesan cheese until melted and combined.
Serve hot.