Bring to a boil. Reduce heat; cover and cook for 15 minutes or until tender. Meanwhile, in a small saucepan, combine the onions, green pepper, water, oil and bouillon. Bring to a boil. Reduce heat; cover and simmer for 8-10 minutes or until vegetables are tender. Drain the potatoes; add onion mixture, tomatoes and oregano.
Stir gently to coat.