Heat the olive oil in a large pot over medium heat.
Add the diced onions and cook until they are translucent, about 5 minutes.
Stir in the minced garlic, carrots, and celery and cook for another 3-4 minutes.
Add the zucchini, bell pepper, and continue cooking for another 5 minutes, stirring occasionally.
Pour in the diced tomatoes with their juices and the vegetable broth.
Add the green beans, basil, and oregano. Season with salt and pepper to taste.
Bring the mixture to a gentle boil, then reduce to a simmer and cover.
Cook for about 15-20 minutes, until the vegetables are tender.
Stir in the chopped spinach or kale and cook for an additional 5 minutes.
Taste and adjust seasoning if necessary before serving.