Heat olive oil in a large pot over medium heat. Sauté onion, garlic, carrots, and celery until softened, about 5 minutes.

Add ground turkey, breaking it up with a spoon. Cook until browned and no longer pink.

Stir in oregano, salt, and pepper; cook for an additional minute.

Pour in chicken broth, scraping any bits from the bottom of the pot. Bring to a gentle boil.

Reduce heat and let simmer uncovered for 20 minutes.

Serve hot, topped with grated parmesan or fresh basil if desired.