Wash and peel the vegetables. Dice the onion, carrots, and zucchini into small, even pieces. Chop the celery and green beans. Mince the garlic finely.
Heat the olive oil in a large pot over medium heat. Add the diced onion and sauté for 5 minutes until translucent. Stir in the minced garlic and cook for an additional minute.
Add the diced carrots, celery, zucchini, and green beans. Sauté for 5-7 minutes until they start to soften. Pour in the diced tomatoes and vegetable broth. Stir in the dried oregano, basil, salt, and pepper.
Bring the mixture to a boil, then reduce the heat to low and let it simmer for 20-25 minutes.
Add the fresh spinach and lemon juice. Stir until the spinach wilts, about 2 minutes. Taste and adjust seasoning if needed. Serve hot.