In 1985 and 1986, he served as the assistant announcer at Laurel Park, Pimlico, Bowie and Timonium Racetrack in his native Maryland.
Collmus' move to a major summer racing circuit occurred in 1994 when he became the announcer at Monmouth Park, host of the 2007 Breeders' Cup.
On August 13, 2014, Collmus was announced to once again succeed Tom Durkin, this time as the voice of the New York Racing Association.
[3] Collmus called races at Del Mar in 2020 as regular track announcer Trevor Denman did not attend due to the COVID-19 pandemic.
[6] In March 2023, it was announced that Collmus would call the 2023 Dubai World Cup Night at Meydan Racecourse, replacing the regular Emirates Racing Authority caller Alistair Cohen.
Cohen stated that the deal to hire Collmus was done behind his back and in response he terminated his ERA contract with immediate effect and returned to his native South Africa.
[7] On July 19, 2023, Dennis Drazin, Chairman and CEO of Darby Development LLC bestowed upon Collmus, a 20-year Monmouth Park Racetrack announcer, the 2023 Bill Handleman Award for his work on 2023 $1 million Haskell Stakes (Grade 1).
[8] Collmus earned national notice when on August 22, 2010, he called a race at Monmouth Park featuring two horses named Mywifenosevrything and Thewifedoesntknow.
(Monmouth Park - August 22, 2010 - Race 7)Collmus' stretch call attracted worldwide attention[9] and earned hundreds of thousands of views on YouTube.
In Collmus' 14th consecutive Kentucky Derby, his stellar stretch-finish line call did freeze not only the glory of Mystik Dan vis-à-vis the twin fate of Sierra Leone and Forever Young but a historical and "shining moment" for American racing.