Heat a large pot over medium heat and add a splash of olive oil.
Sauté the chopped onion until translucent, about 3-4 minutes.
Stir in the diced carrots and celery, cooking for another 5 minutes.
Add the minced garlic and sauté for an additional minute.
Pour in the broth and bring to a boil.
Once boiling, add the diced tomatoes and oregano.
Reduce heat and simmer for about 10 minutes.
Stir in the pastina and cook until al dente, about 5 minutes.
Season with salt and pepper to taste.
Garnish with fresh parsley before serving.