Kay, who presents C4's youth strand T4, won the top spot just months after joining the station, where he has fronted the 'Happy Hour' slot on Sunday afternoons.
His new slot runs from 10am-1pm Saturdays and Sundays and, according to a Radio 1 spokesman, will be the "usual music-led type of show with entertainment chat". Kay will begin his new weekend show on March 27.
"I've only been at the station for a couple of months so I am pretty chuffed that they have agreed to give me a bigger slice of the Radio 1 pie. I promise to be careful with it," Kay said.
Northerner Kay, who was signed in October by Radio 1 controller Andy Parfitt, co-hosts the C4 youth strand T4 with June Sarpong. He also hosted Chris Evan's failed 'Boys and Girls' before it was axed by Channel 4 bosses.
Princess Talent, Kay's agents, were unavailable to comment on whether he will also remain at T4.
Bowman and Murray are moving to a new weekday show, made possible by the impending departure of Mark & Lard.
Mancunians Mark & Lard present their last show on March 26 after 10 years with the station, before moving to Radio 2 and BBC 6 Music respectively.
In addition to the latest round of changes, the breakfast show's Comedy Dave will be teaming up with Mark 'Chappers' Chapman from the Sara Cox show for a Sunday programme.
Cox is being replaced by Scott Mills when she goes on maternity leave.
Cox, who is married to club DJ Jon Carter, has booked time off at the end of May to have the couple's first baby. Southampton-born Mills, 29, will swap his weekend afternoon slot for drivetime when Cox is away.
The changes are part of a wide reshuffle designed to shake up the station's flagging audience figures. The station had 9.4m listeners in the final quarter of last year, down from 9.85m in the previous quarter and 10.5m at the end of 2002.
A Radio 1 spokesman said that the reshuffle was part of Andy Parfitt's strategy to "provide listeners aged 15 and 24 with young, fresh, exciting broadcast talent".
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