Heat the oil in a large saucepan and fry the onion, celery and pepper over a medium heat for 10 minutes, stirring regularly.
Add the garlic and thyme and stir for 2 minutes. Stir in the tomato paste and cook for 2 minutes.
Gradually incorporate the stock and bring to the boil.
Add the potato and quinoa and simmer for 15 minutes.
Add the beans and sweetcorn and simmer for 5 minutes or until the vegetables are tender and the quinoa has thickened the soup.
Season to taste with salt and pepper and serve in enamel mugs.