Quarrington's most consistent musical colleague has been Martin Worthy; their friendship began in high school. He was also a high school friend of songwriter Dan Hill, with whom he reunited toward the end of his life to collaborate on musical projects. Quarrington collaborated with many artists (a defining element of his overall body of work) who achieved recognition in their respective disciplines. These include Nino Ricci, Joseph Kertes, Dave Bidini, Jake MacDonald, John Krizanc, Christina Jennings, Judith Keenan, Michael Burke, Peter Lynch, Ron Mann, Robert Lantos and many others.