In mid-1985, 23-year-old Scheff joined the multi-platinum band, Chicago, after Peter Cetera had departed the band to continue his solo career. His lead vocals were debuted on the 1986 single "25 or 6 to 4," a remake of their 1970 hit, then followed up with "Will You Still Love Me?" which became one of Chicago’s biggest hits.
In addition to performing the band's classic material, Scheff had composed several original songs for the band, including their 1989 Top 5 single "What Kind of Man Would I Be?".
Scheff also co-wrote the song "Heart of Mine" with Bobby Caldwell and Dennis Matkosky. The song became a big hit for Boz Scaggs in 1988 and was included in the 1988 Boz Scaggs album "Other Roads" and the collection Hits!.
Scheff, along with co-writers Peter Wolf and Ina Wolf, wrote the song "Bigger Than Elvis" in 1993 for what was intended to be Chicago's 22nd album. This song is about his father, Jerry Scheff, describing Jason's childhood memories of watching his father play on television as Elvis Presley’s bass player. The album however, was rejected by Warner Brothers in 1993, and remained unreleased until 2008 when Rhino released it as Chicago XXXII: Stone of Sisyphus.
In 2005, Scheff’s frequent trips to Nashville writing new material became the spark to light the flame to record Chicago XXX, their first collection of new material since 1991's Twenty 1. Scheff also enlisted Rascal Flatts vocalist and bassist Jay DeMarcus to serve as producer for the new album, which was released on March 21, 2006. Scheff co-wrote seven of the twelve songs on the CD.
Scheff has also recorded as a solo artist, releasing a CD entitled Chauncy in 1996, as well as several duets released only in Japan. He is also collaborating with Jay DeMarcus on several projects including a solo album with Jay DeMarcus as producer.
He would be part of 2 acapella releases by a band dubbed "West Coast All Stars". The first in 1997 called "California Dreamin'" included vocals by Joseph Williams, Bill Champlin, Bobby Kimball & Scheff; the second in 1998, "Naturally", again would feature Williams, Kimball and Scheff adding this time Tommy Funderburk as the fourth vocal.
The 2013 Oscar Nominated Nebraska (film) featured the Chicago composition "We Can Last Forever" highlighting Scheff's lead vocals and penned by himself & John Dexter.
In 2014, Chicago released “Chicago XXXVI: Now”, a studio album of original songs, where Scheff produced, co-wrote and performed the title track.
A few weeks after performing with Chicago for their Rock and Roll Hall of Fame Induction in April
2016, Jason Scheff took the opportunity to go home and take care of his family.
He has gotten heavily involved in charity work mostly in the Celebrity Golf realm.
Top Hits Include:
Will you Still Love Me?
I Don’t Wanna Live Without Your Love
You Come to My Senses