I have Google search engines installed in Firefox 3.6, IE 8, and Google Chrome 5.0.
Is there a program that can delete all this search history at the same time in these three browsers?
CCleaner is a free solution for this - find it at http://www.piriform.com/ccleaner.
You might also want to check out Auslogics Boost Speed at http://www.auslogics.com which is a decent set of PC utilities that includes a privacy program that erases browser history and many other categories of PC usage info.
There are many programs that clean various things - search, browsing, download, or URL history. Some of these programs have cleaning scheduler that can clean at once all search history in many browsers.
I recommend to you - Mil Shield software because this program cleans automatically all web/search history in 6 popular browsers.