Newill, one of Hollywood's most underappreciated singing cowboys, embarked on his career as a tenor with the Los Angeles Light Opera company in the early 1930s. By the mid-decade, he took the stage as a vocalist with various society orchestras, including those of renowned bandleaders such as Gus Arnheim, Phil Harris, and Eddy Duchin. His impressive vocal talents also led to a brief stint on the Burns & Allen radio show, broadcast by CBS, as well as a spell in vaudeville.
In 1937, his exceptional talent was spotted by a talent scout, marking the beginning of his journey on the Hollywood western trail. His first stop was the Poverty Row outfit Grand National, where he starred in the popular boys' adventure yarn Renfrew of the Royal Mounted. Following the initial two installments, Newill appeared as the titular hero in another five films for Monogram, with production values gradually declining.
Between 1941 and 1942, he was loaned out to Fox and RKO, making Decca recordings with the esteemed Victor Young Orchestra. He then surfaced as Texas Ranger Jim Steele in 14 low-budget westerns for the bottom-of-the-drawer company PRC. During filming breaks, he and co-star Dave O'Brien experimented with goat farming.
In 1944, Newill was replaced by Tex Ritter and left the range and screen acting for the bright lights of the New York stage. In the 1950s and 60s, he pursued a variety of occupations, including operating a sawmill, disk-jockeying for a classical radio station, running a kiddies' ride business, and even attempting to manufacture fiberglass speedboats, though with limited financial success. He eventually retired in 1971.