Hi, " a couple of years ago " is the right phrase.
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lfcforeverWhat is correct?
KooyeenHi,
quoted from Merriam-Webster's Learner's Dictionary (http://www.learnersdictionary.com):
a couple
informal 1 : two or a few of something
Note: In informal U.S. English,
Kooyeen
So as MrPernikety said, both are ok, and "of" can be left out in informal American English (and maybe in British English too, but I'm not sure).