Put quinoa in sieve and wash thoroughly under cool running water, at least 1 minute. Drain. Cook quinoa in a medium pot of well-salted boiling water, uncovered, until almost tender, about 10 minutes. Drain in sieve, then set sieve over same pot above 1 inch of simmering water. Cover quinoa with a folded kitchen towel (not terrycloth), then cover with a lid (don't worry if lid doesn't fit tightly). Steam until tender, fluffy and dry, about 15 minutes. Let stand off heat, without lid but still covered with towel, 5 minutes.

Meanwhile, soak onion in a bowl of cold water 5 minutes, drain well and pat very dry.

Whisk together vinegar, oil, 1/2 t. salt and 1/4 t. pepper in large bowl. Toss quinoa, onion, jicama and parsley with dressing.