Williams is responsible for a number of enduring pop hits from the 1970s, including "(Just an) Old Fashioned Love Song", a U.S. top-ten hit for the band Three Dog Night in late 1971, and a number of Carpenters hits, most notably "We've Only Just Begun", which has since become a cover-band standard and de rigueur for weddings throughout North America. An early collaboration with Roger Nichols, "Someday Man", was covered by The Monkees (a group for which he auditioned but was not cast) on a 1969 single, and was the first Monkees' release not published by Screen Gems.
A frequent cowriter of Williams was musician Kenneth Ascher; their songs together included the popular children's favorite "The Rainbow Connection", sung by Kermit the Frog in The Muppet Movie. Most recently, he collaborated with Scissor Sisters on their sophomore album, Ta-Dah.
He is a member of the Songwriters Hall of Fame, and his songs have been performed by both pop and country music artists. He has won one Academy Award, two Grammy Awards and several Golden Globes.