Leroy moved to Chicago in 1952, where he spent a year as the house bass player at the Beehive jazz club, playing with local and visiting artists, including saxophonist Charlie Parker. In 1954, he headed west for Los Angeles, where he immediately made an impact on the local music scene, then in the middle of the "cool jazz" boom. In Los Angeles, he worked with the great Art Tatum as well as with almost all the major figures associated with the West Coast style, including Chet Baker, Stan Getz, Shorty Rogers, Herb Geller, Serge Chaloff, Art Pepper, Harold Land, Russ Freeman and Carl Perkins (the pianist, not the rock and roll singer), with whom he had gone to school in Indianapolis.

Vinnegar’s most famous association of the era was with pianist Andre Previn and drummer Shelly Manne on the best-selling album My Fair Lady, a jazz version of tunes from the show released in 1956 on Lester Koenig's influential Contemporary label. As well as becoming a mainstay of the local scene, he also played regularly with visitors to the coast, and recorded with Sonny Rollins in that context on Sonny Rollins and the Contemporary Leaders in 1959.