Enrolled Agent
EA, QPA, CHFC, CEBS, CLU - 30 years experience providing financial advice
If you wrote a covered call then the option income will be added to the stock proceeds when the call is exercised and will be treated the same as your holding period for the stock. If you held the stock for more than 1 year then the option income is considered long term capital gain, the same as the gain on the stock. If you held the stock 1 year or less then income and gain will be considered short term.
See page 57 - http://www.irs.gov/pub/irs-pdf/p550.pdf