They were signed to Warner Bros. Records by producer Lenny Waronker, and scored one of the sunniest hit singles of the 1967 "Summer of Love" with a version of Paul Simon's "The 59th Street Bridge Song (Feelin' Groovy)", which climbed into the Top 20 of the national record charts. Their first album, boasting the arranging skills of Leon Russell and the composing talents of Randy Newman, backed by Harpers' exceptional vocal talent, proved an enticing debut.

Their brand of wistful, "Roaring Twenties pop" enjoyed only a brief vogue, roughly from late 1966 to mid-1967, but they managed to get a few more minor chart singles, notably Van Dyke Parks's "Come To The Sunshine" and covers of "Anything Goes" and "Chattanooga Choo Choo."

The band enjoyed successful tours and released four albums before changing musical tastes finally forced them into disbanding in 1970. Ted Templeman went on to become one of Warner Bros.' primary staff producers, working with the Doobie Brothers, Van Morrison, Van Halen and others. In 1976, three members reunited to record the album, "As Time Goes By", which made little impact and was to be the group's last original recording. "Feelin' Groovy: The Best of Harpers Bizarre" was issued in 1997.

Drummer John Petersen suffered a fatal heart attack on November 11, 2007.