Heat oil in a large heavy bottom pot over medium heat. Add onion and pepper to the pot and saute until onions are translucent about 5 minutes. Add taco seasoning to the pot and cook for an additional 2 minutes.
Pour diced tomatoes, black beans, corn, and chicken broth into the pot and stir. Nestle the chicken breasts into the pot and increase heat to high.
Bring the soup to a boil, reduce to a simmer, cover and simmer for 30 minutes.
Remove chicken from the pot and shred with two forks. Stir shredded chicken back into the soup along with the sour cream.
Serve soup with your favorite toppings like shredded cheese, cilantro, lime juice and tortilla chips.