The creation of a new orchestra for him in 1991 shaped much of his thinking for the next fifteen years. With the Hollywood Bowl Orchestra (a hand-picked ensemble, selected by Mauceri, from Hollywood's best studio musicians) and its huge outdoor venue, Mauceri continued to develop programming ideas first attempted at Yale in the late 1960s. In addition, his work in Berlin connected his research with the lives of many Hollywood composers who had escaped Hitler's Europe. During his summers at the Hollywood Bowl he brought dance companies and opera performances back to the venue after years of neglect. In addition, he instituted film nights in which music written in Los Angeles was given world concert premieres, sometimes synchronized to excerpts on the screen and sometimes within a concert program. In order to do this, Mauceri had to edit and create performing versions of literally hundreds of hours of music. In addition to celebrating the music written in Los Angeles and putting it into larger contexts, he has brought fully staged musicals to the Bowl for the first time in its history. Within the contexts of his enormously popular programming, he has played Bowl premieres of works by Arnold Schoenberg, John Adams, John Corigliano and Gyorgy Ligeti, among many others. Mr. Mauceri developed direct professional and personal relationships with a number of important film composers, like Miklos Rozsa, David Raksin, Elmer Bernstein, Danny Elfman, and Alan Menken, as well as Adam Guettel, all of whom have been celebrated by Mauceri. A number of them have written new works for him, including symphonic suites from Cabaret and Chicago by John Kander, September 11, 2001 by Jerry Goldsmith, a symphonic suite from Ragtime by Stephen Flaherty, A Fanfare for John at the Bowl by Elmer Bernstein (his last composition) and Three Symphonic songs from The Light in the Piazza by Adam Guettel.
Mr. Mauceri's relationship with Mr. Guettel goes back to a time when the very young Guettel was the principal boy soprano at New York City Opera. During Guettel's Yale undergraduate years, he frequently sat in the pit for performances led by Mr. Mauceri of On Your Toes, which was composed by his grandfather, Richard Rodgers. Mr. Guettel served as Mr. Mauceri's assistant in Macerata, Italy (Rigoletto) as well as with a number of European orchestras.
Mauceri and his Hollywood Bowl Orchestra made thirteen recordings for Philips, many of which have won awards, and toured Japan four times and Brazil once. His average audience at the Bowl was well over 12,000 patrons per concert for over sixteen seasons. Between September 17 and 21, 2004 alone, his four concerts brought in a total of 70,000 patrons. For his 250th concert with the Bowl Orchestra, the governor of California proclaimed August 31, 2002 "John Mauceri Day" in the state.
Mauceri, who was originally called conductor of the Bowl Orchestra, subsequently became its principal conductor. In announcing his final season (2006), the Los Angeles Philharmonic honored him with the lifelong title of Founding Director. For his final season, Mauceri has commissioned new works by Richard Rodney Bennett, Danny Elfman and Adam Guettel. He was given permission by the Walt Disney Company to perform the original Fantasia live to film for the first time in America and he has also presented segments left unfinished in 1940. In addition, he conducted a staged concert performance of Sunset Boulevard with the Academy Award winning score of Franz Waxman synchronized to the dialogue, all performed live for the first time in history, and celebrating the centenary or both Waxman and director/writer, Billy Wilder. In effect, this concert created a new genre, combining live performance of a screen play with its complete orchestral score. In June of 2007, Mr. Mauceri was inducted into the Hollywood Bowl Hall of Fame, along with Placido Domingo.