Moyles, who has grown the breakfast show's reach from 5.93m to 7.26m listeners since taking over in 2004, will now do a three and a half hour show from 6.30am to 10am.
The changes are aimed at focusing on output for younger listeners, according to Andy Parfitt, controller of Radio 1, 1Xtra and Teens.
Parfitt said: "It's important that we keep up the pace of change and innovation both on air and online. This simplifies and strengthens Radio 1 and is an important step in providing programmes focussed on the under-18 audience."
Kelly Osbourne, famous for her appearance in reality TV series 'The Osbournes', takes over the 10pm to 12pm 'Surgery' programme from Annie Mac, who will now helm the three-hour slot before this.
The 'Chart Show' is also affected by the changes, with JK and Joel leaving the station and Fearne Cotton and Reggie Yates taking over the show. The pair had previously hosted the weekend show, which the pair took over from DJ Spoony last year. They are being succeeded by Nihal.
JK and Joel's early breakfast slot has been handed to a new arrival from student radio, Greg James.