Put olive oil in the bottom of a heavy bottomed soup pot, and heat over medium high heat. Add onion and garlic, and sauté until onion is transparent, about 3-5 minutes.
Add cooked chicken, oregano, cumin, chili powder, salt and black pepper, and continue to sauté for about 3 more minutes until spices are distributed.
Add chicken broth and green chiles, and bring to a boil. Reduce heat to simmer, and cook for about 15 minutes until onions are softened.
Add beans and continue cooking for 5 minutes. Remove from heat and add chopped cilantro.
Serve chicken chili with optional garnishes such as tortilla chips, shredded cheese, sour cream, sliced jalapeño, chopped tomato, lime wedges, diced avocado, cilantro leaves or sliced green onion.