Microsoft has been on a tear since mid-April, and option activity was heavy to the bullish side going into yesterday's holiday.
OptionMonster's tracking programs detected strong activity in the September 37 calls with less than 45 minutes left in Wednesday's shortened session, as big chunks traded for $0.32. More than 5,100 of the contracts changed hands, almost double the previous open interest, indicating that these are new positions.
These calls lock in the price where shares can be bought in the software giant. Investors use the options to get cheap upside exposure and generate leverage to the stock price in a rally.
Microsoft rose 0.07 percent to $34.01 and is not far off its highs for the year. Because Wednesday's traders were buying calls in the September expiration, they are giving the stock some time to make a move.
Overall calls in the name outpaced puts by about 22,000 to 12,500 in the session.
—By CNBC Contributor Pete Najarian
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Pete Najarian is a professional investor, CNBC contributor, regular co-host of CNBC's "Fast Money" and co-founder of OptionMonster.com. Najarian has no positions in MSFT.