Heat the olive oil in a large pot over medium heat.
Add the chopped onion and sauté until translucent.
Stir in the minced garlic and cook for another minute.
Add the sliced carrots and chopped celery; cook for 5 minutes.
Incorporate the diced zucchini and green beans into the pot.
Pour in the diced tomatoes and vegetable broth.
Season with oregano, salt, and pepper.
Bring the mixture to a boil, then reduce heat to low.
Simmer for 20-25 minutes, or until vegetables are tender.
Taste and adjust seasoning if necessary.