If you have time before cooking try soaking your quinoa for a couple of hours. It will cook faster and also make it easier to digest. Make sure you rinse and drain it well before adding to the stew.
Also, if you are going to cook this in advance don't put the greens in until just before serving, they will go a bit dull otherwise!
Stew is perfect batch cooking as it can be frozen, defrost fully before reheating to a hot temperature!