In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté for about 5 minutes until softened.
Stir in the minced garlic and cook for an additional minute until fragrant.
Add the carrots, celery, zucchini, and red bell pepper to the pot. Sauté for 5-7 minutes until the vegetables start to soften.
Pour in the diced tomatoes with their juice and the vegetable broth. Stir in the green beans, oregano, basil, salt, and pepper. Bring the mixture to a boil.
Reduce the heat to low and let the soup simmer for 20 minutes, stirring occasionally.
Add the frozen peas and fresh spinach, cooking for an additional 5 minutes until the spinach is wilted.
Taste and adjust seasoning if necessary. Serve hot, topped with grated Parmesan cheese if desired.