After the Jones band broke up in 1936, Jenkins worked as a freelance arranger and songwriter, contributing to sessions by Isham Jones, Paul Whiteman, Benny Goodman, Andre Kostelanetz, Lennie Hayton, and others. In 1938, Jenkins moved to Hollywood and worked for Paramount Pictures and NBC, and then became Dick Haymes' arranger for four years. In 1944, Jenkins had a hit song with "San Fernando Valley". In the 1940s, he was music director for the radio version of the program "Mayor of the Town", and his orchestra provided the music for Ransom Sherman's program on CBS.