The 26-year-old former Aberdeen and Dundee player was most recently with Derry City but now returns to the SPFL and could make his debut away to Inverness CT on January 5.
QOS boss Gary Naysmith told the club website: "Nicky had a few offers from other Championship clubs so I am pleased he has agreed to sign for us.
"He hasn't played competitively since October when the Irish league finished but it won't take him long to get up to full match fitness."
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