In a large saucepan, saute onion and oil over medium-low heat until tender.
Add carrots, green beans, and potatoes, and saute another 5 minutes.
Add tomatoes and 2 cups water, turn heat to high, and bring to a boil. Boil 2 minutes, then remove from heat. Transfer tomatoes to a bowl or plate and let cool.
Peel tomatoes and return to sauce pan.
Add wine, oregano, salt, pepper, and simmer until vegetables are tender, about 30 minutes.
Bring to a boil, add orzo, simmer until pasta is tender.
Add lemon juice and fresh basil. Adjust salt and pepper, if necessary.
Serve immediately.