Stephenson, who is expected to join the Richard Desmond-owned group within the next month as celebrity magazine advertising controller, will report to Stan Myerson, group joint managing director at Northern & Shell.
She will oversee OK!, Star and New! magazines.
Stephenson will be in charge of around 20 staff, including a group of researchers.
Prior to her time working at SkyMag, Stephenson was advertising director at News Magazines, which she joined in January 2006.
Stephenson's duties were previously handled by a number of group heads, who reported to Melanie Danks, Northern & Shell's group head of trading.