First recorded by The Hombres (US #12 1967).
Other hit version by Jonathan King (UK #26 1969).
Also recorded by John Mellencamp (1989).
From the wiki: “Formed in 1966, The Hombres comprised Jerry Lee Masters, Gary Wayne McEwen, B. B. Cunningham, Jr., and John Will Hunter. ‘Let It All Hang Out’ was written by Masters, Hunter, McEwen and Cunningham. The song’s spoken intro – ‘A preachment, dear friends, you are about to receive on John Barleycorn, nicotine and the temptations of Eve’ – dates to the 1947 novelty recording ‘Cigareetes, Whuskey and Wild, Wild Women’ by Red Ingle and His Natural Seven. ‘Let It Hang Out’ has been used in a US advertising campaign for Foster’s Lager and included on the compilation album Nuggets: Original Artyfacts from the First Psychedelic Era (1972). The song was also covered – with much the same production arrangement – in the UK by Jonathan King (‘Hooked On a Feeling‘, ‘Everyone’s Gone to the Moon’) in 1969, and also appeared on his 1989 compilation album, The Butterfly That Stamped. Yet another cover version was recorded by The Nails in the mid 1980s. The song also appears as a hidden track on John Mellencamp’s 1989 album Big Daddy.”
Jonathan King, “Let It All Hang Out” Top of the Pops TV performance (1969):
John Mellencamp, “Let It All Hang Out” (1989):