Frost expanded Grand Funk's "power trio" musical style, by adding another dimension to their music. Grand Funk scored its biggest hits after Frost joined the band in 1973, and his work is instantly recognizable on Grand Funk's #1 songs "The Loco-Motion" (a cover of Little Eva's hit) and "We're An American Band". He also contributed significantly to Grand Funk as a songwriter, in partnership with drummer Don Brewer.
After the initial breakup of Grand Funk in 1977, Frost joined with former Grand Funk bandmates Brewer and Mel Schacher to form the short-lived band Flint. After the demise of Flint, Frost joined Seger's Silver Bullet Band, where he has remained for over two decades. In July 2005, Frost "sat in" at a concert in North Branch, Michigan, for the first time since 1977 with Grand Funk. He has done so a number of times since, at such locations as Detroit and Las Vegas.