Heat oil in a large pot over medium heat. Add pumpkin, onion, capsicum, carrots, chilli, celery and garlic. Cook for 5 minutes. Add taco seasoning and cook for a further 2 minutes.
Add tomatoes, kidney beans, corn, stock and chilli flakes. Reduce heat to low and cook for 30 minutes.
Serve over rice, with grated cheese and sour cream or Greek Yoghurt if desired.