The restructuring comes less than six weeks after Miller was appointed to the Internet unit of media conglomerate AOL Time Warner, to shore up performance of the unit and do away with trouble spots that have kept the company in recent headlines.
The new structure will allow AOL to focus on new content and features, a "differentiated broadband" service and profitability in international units.
Miller is set to take a direct role in overseeing the AOL brand, interactive marketing and broadband initiatives.
The role of AOL president and chief operating officer are being eliminated, and AOL executive vice-president and chief financial officer Joseph Ripp will take a leading role as the new AOL vice-chairman. Ripp will oversee corporate and operating functions, including AOL's network and technologies.
Current AOL president Ray Oglethorpe is set to retire after a transition period in which he will serve as a company adviser.
Meanwhile, current chief operating officer Michael Kelly will move to AOL International as its chairman and chief executive officer.
In other changes, AOL said that it is reassigning employees of the company's business affairs unit to the specific groups they serve. The business affairs unit has been the subject of scrutiny lately amid accusations that it forged a number of unusual deals in order to enhance the performance of AOL's advertising business artificially.
AOL Time Warner admitted last month that it had discovered three deals in which it may have inappropriately booked some $49m (£31.4m).
A prolonged weakness in the online advertising market has taken its toll on the Internet unit in recent quarters, along with sluggish subscriber growth. The company's new organisation under Miller seeks to focus on broadband opportunities and refreshing its blotched image.
Don Logan, chairman of AOL Time Warner's Media and Communications Group, said that restructuring will make AOL's operating units more "nimble" and "accountable".