Brian Doherty, in his book Radicals for Capitalism quotes Leonard Read, founder of the Foundation for Economic Education, as saying:

So far as I am concerned, I can see no hopes whatever for [MPS] to become a useful force in the fight for freedom… the philosophies range all the way from middle-of-the-roaders to one who is an out-and-out socialist.

This was, I believe, in 1949, after the first Mont Pelerin Society meeting.  The Mont Pelerin Society was intended to be a classically liberal organization.  It vaguely describes its own mission statement accordingly:

Its sole objective was to facilitate an exchange of ideas between like-minded scholars in the hope of strengthening the principles and practice of a free society and to study the workings, virtues, and defects of market-oriented economic systems.

Given the organization’s purpose, it is unlikely that any of the original MPS attendees were “socialist” in the sense that they supported complete government control of the means of production for the purpose of equalization of income.  More likely they merely supported, as Mises complained, government controlled redistribution and Hayekian programs to guarantee a “minimum standard of living”.

If so, this is more anecdotal evidence for what I assert is a more commonly used alternative definition of “socialism” – generally, programs of mandatory redistribution run by the government.