At the age of 18, within two months of becoming the first freshman student at Northwestern University of Chicago Symphony Principal horn, Dale Clevenger, William VerMeulen was employed as an extra horn with the Chicago Symphony. Three months later, VerMeulen won his first professional orchestral audition as Second Horn of the Kansas City Philharmonic. Almost immediately after his arrival, the orchestra went on strike and ceased to play concerts. During the strike VerMeulen performed with the Jack Daniels Original Silver Cornet Band and spent 4 months as an acting Principal Horn of the St. Paul Chamber Orchestra. He was also offered Principal positions at the La Scala Opera and Hamburg State Philharmonic orchestras, which he declined to accept. Shortly after returning to Kansas City when the strike was resolved he won the Principal Horn position of the Honolulu Symphony Orchestra, a title he held for 8 seasons. VerMeulen then won Principal Horn in the Columbus Symphony and shortly thereafter was hired by Christoph Eschenbach and the Houston Symphony as Principal Horn.
VerMeulen was the second American Hornist to record the complete Mozart Horn Concertos with a major American Orchestra. The album was recorded at with Christoph Eschenbach and the Houston Symphony in 1993. In addition, he was featured on Cantos, a CD of works by American composer Samuel Adler and a recording of the chamber version of Bruckner 7th symphony performing with Gruppo Montibello. In addition to the dozens of recording made as Principal Horn in an orchestra he has recorded the Brahms Trio opus 40, Mozart Quintet K. 407, Schoenberg Wind Quintet, Beethoven Septet opus 20, Spohr Nonet opus 31, and the Six Bagatelles for wind quintet by Ligeti for Music@Menlo. In addition, he is featured as first horn on a live recording of Bach Brandenbug Concerto no. 1 with the Chamber Music Society of Lincoln Center. He is also featured on the CD, "Texas Horns" which is a collaboration between the horn sections of the Houston and Dallas Symphony Orchestras. VerMeulen has had numerous compositions written for him, including concerti by esteemed American Composers Samuel Adler, Pierre Jalbert, Anthony DiLorenzo and the 'horn cantata' Canticum Sacrum written by Robert J. Bradshaw. He also performed in the North American premier of Collage for four horns and orchestra by film composer James Horn. VerMeulen has concertized nationally and internationally as soloist with the Auckland Philharmonia, Wroclaw Philharmonic in Poland, the Savannah Symphony, Toledo Symphony, Buffalo Philharmonic, Chicago Civic Orchestra, Lake Forest Symphony, Anchorage Symphony, Jalapa Symphony, Shepherd School Symphony Orchestra, Huntsville Symphony, Virginia Symphony, Kraków Chamber Orchestra, National Symphony of Mexico, National Philharmonic, Columbus Symphony, Sun Valley Summer Symphony, Honolulu Symphony and Houston Symphony.
In 1985, he received the "Distinguished Teacher of America Certificate of Excellence" from President Ronald Reagan and the White House commission on Presidential Scholars. He was a member of the Advisory Council of the International Horn Society for six years and serves an adjudicator and board member of the International Horn Competition of America. In 2009-10 he was an artist of the Chamber Music Society of Lincoln Center. As Professor of Horn at Rice University VerMeulen has students who have won positions in the Boston Symphony, Chicago Symphony, Cincinnati Symphony, Cleveland Orchestra, New York Philharmonic, Detroit Symphony, National Symphony Orchestra, National Arts Centre Orchestra, Orchestre symphonique de Montréal, Kansas City Symphony, Seattle Symphony, St. Paul Chamber Orchestra, Colorado Symphony, Detroit Symphony, Toronto Symphony, Dallas Symphony, Houston Symphony, Israel Philharmonic, Los Angeles Philharmonic, San Francisco Symphony, Canadian Brass, as well as many other American and International Orchestras.