Remove skin and bones from rotisserie chicken. Shred the meat and discard the skin and bones.
Preheat the oven to 350 degrees. Melt butter in a large, deep skillet over medium-high heat. Add the onion and sauté until tender. Add the bell pepper and garlic and sauté an additional 3-4 minutes. Stir in broth, soups, tomatoes, chilies, oregano, and chili powder.
Lightly grease a 13x9 baking dish. Layer half the shredded chicken and half the soup mixture. Top with half the tortilla chips and half of the cheese. Repeat layer.
Cover lightly with aluminum foil and bake for 1 hour, or until bubbly. Remove foil during the last 10 minute of cooking.
Remove from oven and let cool for 10 minutes before serving.