The phrase "a gathering of about" is correct and usable in written English.
It can be used when estimating the number of people expected to attend an event or meeting.
Example: "We expect a gathering of about fifty people at the community picnic this weekend."
Alternatives: "a group of approximately" or "an assembly of around".
It was a gathering of about 40 learned men, mostly from the U.S. & the Soviet Union.
Pixar unveiled "Hawaiian Vacation" at a gathering of about 300 Disney investors and analysts in Anaheim, Calif., on Thursday.
"Christian creativity for the present age must not depend on male leaders," she told a gathering of about 700 people.
In June, President Karzai flew to Kandahar to speak to a gathering of about 400 local tribal elders about a pending military operation.
It was one of several protests during the day, including a gathering of about two dozen in front of the Duke Energy Center.
Last week, I posted about my first day at the Clinton Global Initiative in Chicago, a gathering of about 900 leaders from across the country.
The effort will be the first administrationwide initiative run by Mrs. Obama, aides said, and she intends to speak to a gathering of mayors about it next week.
Then she told a gathering of feminists about her own needs that went unmet "betwixt the negro in the south and the white woman in the north, all talking about rights".
Writing about commonplace books ("Narrow Ruled"), Baker gets right to it from the opening sentence ("When I come across something I really like in a book, I put a dot in the margin") and never flags, delivering a gathering of quotations about the gathering of quotations.
And in one scene, Melvin Tolson, the debate coach and union organizer played by Denzel Washington, speaks to a gathering of sharecroppers about how the NLRB offers protection.
In a Las Vegas suburb, at a yearly gathering of about a dozen gay and lesbian friends at the home of Sigrid Brunel and Argentina Kapp, the mood was far cheerier than last year, when anxiety about the coming election and anger about the war in Iraq clouded much of the discussion.
