In a large pot, heat olive oil over medium heat.
Add chopped onion, carrot, and celery; sauté until softened.
Stir in minced garlic and cook for an additional minute.
Pour in the broth and bring to a boil.
Add diced tomatoes and oregano; season with salt and pepper.
Once boiling, add pastina and cook according to package instructions.
Stir occasionally to prevent sticking.
Once the pasta is tender, remove from heat.
Taste and adjust seasoning if necessary.
Serve hot, garnished with fresh parsley.