A prolific, skilled, and versatile lyricist, Bryan collaborated with Tin Pan Alley songsmiths (eg, Alfred Gumble, George W. Meyer, and Al Piantadosi) for hits each year 1906-18 and 1926-8. His "Give Me Your Affection, Honey" was written with Carmen Lombardo. The anti-war song "I Didn't Raise My Boy to be a Soldier," recorded in 1915, became controversial and was banned in Britain and France. Bryan redeemed his popularity with the 1918 patriotic hit "When Alexander Takes His Ragtime Band to France." Many of Bryan's songs, especially "Peg O' My Heart," became standards.
Bryan wrote scores for Broadway shows, eg, The Century Revue, 1919-21. He then moved to Hollywood and wrote songs for motion pictures 1928-49. His "Oui, Oui, Marie" was heard in What Price Glory (1952), and Al Jolson performed the comic "Who Paid the Rent for Mrs Rip Van Winkle?" in Mammy (1930).
Bryan was a founding member of ASCAP (American Society of Composers, Authors and Publishers). Although 230 Bryan songs were registered with ASCAP, it is rumoured that he wrote the lyrics to over 700 songs. He also published a book of poetry, Pagan Love Lyrics (California, 1925). He was inducted into the US Songwriters Hall of Fame in 1970, and was an inaugural inductee into the Canadian Songwriters Hall of Fame in 2003. His song "Come, Josephine in My Flying Machine" was named to the Canadian Songwriters Hall of Fame in 2010.