Begin by microwaving the sweet potatoes on high for about 3 to 4 minutes per potato, heating them just until firm. When they cool enough to handle, peel and cut each potato into 3/4-inch pieces and set aside.
Heat the oil in a large soup pot, then add the onion and garlic and saute over medium heat until golden.
Add the bell pepper, beans, tomatoes, chilies, cumin, and oregano and bring to a simmer. Cover and continue to simmer gently for 15 minutes.
Add the sweet potatoes and continue to simmer until the vegetables are tender, roughly 10 to 15 minutes.