Quinoa is not kitniyos, BUT – in order to be chametz-free, I was told it has to be grown somewhere that is not near chametzdig grains. Some rabbonim therefore hold it should not be used on Pesach, but others who have checked it out, will allow certain brands to be used. It’s kind of like how mushrooms need a special hechsher for Pesach.
My husband likes it, but it makes me barf. Though it looks somewhat like cous cous (which I do like), it has a weird texture and taste, even when prepared properly by an appetizing store, that I just cannot warm up to (sorry for splitting my infinitives, again).