Heat the olive oil in a large pot over medium heat. Add the onion, garlic, carrots, and celery. Cook for 5 minutes until the vegetables begin to soften.
Stir in the zucchini and cook for 2 more minutes.
Add the diced tomatoes, vegetable broth, quinoa, cannellini beans, oregano, salt, and black pepper. Bring the mixture to a boil.
Reduce the heat to low, cover the pot, and simmer for 15 minutes until the quinoa is tender and the vegetables are cooked through.
Taste and adjust salt or pepper if needed. Ladle into bowls and top with fresh basil leaves before serving.