Powell started working at UCLA in the acquisitions department of the library in 1938. He was University Librarian at the UCLA Library from 1944 to 1961, and head librarian of the William Andrews Clark Memorial Library from 1944 until 1966. He was the first dean of the School of Library Service at UCLA, which later merged to become the Graduate School of Education and Information Studies. He was also a lecturer in English at UCLA and a visiting professor at the Columbia University School of Library Service. Under his directorship, the UCLA library "quadrupled in size," numbering some 1.5 million volumes circa 1960. He acquired "such noted collections as Michael Sadleir's Victorian Fiction and the 80,000-volume library of C.K. Ogden, originator of Basic English."