Add butter to a large stock pot or Dutch oven.
Place over medium heat.
When butter has melted and is hot, add onions, carrots, celery and oregano. Sauté until tender.
Add flour. Stir to incorporate -- to form a roux.
Add minced garlic, chicken broth, marinara sauce, potatoes and tomatoes. Bring to a boil. Immediately reduce heat to a simmer.
Add zucchini, yellow squash and garbanzo beans. Simmer for 5 minutes.
Taste. Add salt and pepper, to taste.
Simmer for 15 more minutes.
Stir in escarole or romaine, basil, Romano and Parmesan cheese.
Continue to stir until lettuce has wilted and cheese has melted and is fully incorporated.
Simmer for 10 minutes.
Taste. Add more salt and pepper, to taste, if needed.
Serve hot.