Heat the olive oil in a flameproof casserole dish or a large, deep frying pan over medium heat. Add the onion and capsicum and cook for 3 minutes until softened.
Add the quinoa, chickpeas, tomatoes, corn, chilli flakes, cumin and 2 cups of water and stir well to combine. Increase the heat to medium–high and cook, covered, for 15 minutes until the quinoa is tender.
Transfer the quinoa mixture to a serving dish, if necessary.
Finish with a squeeze of lime juice and a sprinkling of coriander and serve with the mashed avocado on the side.
Store any leftovers in an airtight container in the fridge for 3−4 days or freeze for up to 3 months.