Berger, 51, brings 34 years of professional experience to Miami, including the past five with the D-backs. McAvoy was a special assignment scout with the Rays.
In Arizona, Berger worked as a special assistant to the GM and a Major League scout. He assumed player-development duties in 2009, when A.J. Hinch was promoted to manager. A year later he was named Arizona's director of pro scouting, charged with overseeing the organization's scouting at the Major League and Minor League levels.
McAvoy joins the Marlins after spending the past four years with the Rays. From 2006-09, he was a pro scout with the Astros.
Berger also has a longstanding relationship with Marlins owner Jeffrey Loria.
When Loria owned Oklahoma City's Triple-A team, Berger was in that organization, and their paths also crossed when Loria owned the Montreal Expos.
Berger played Minor League ball from 1980-93, and he has experience coaching and managing in the Minors.
After transitioning from coaching to scouting, Berger worked for the Astros, Rockies and Blue Jays.
McAvoy, who pitched at the University of Mississippi, had a brief (2000-03) Minor League career with the Expos.
Drafting and developing are big parts of the Marlins' plans moving forward, and an offseason objective has been to beef up personnel.
In addition to Berger and McAvoy, the Marlins recently hired Craig Weissmann, formerly with the A's, now Miami's vice president of player personnel.
Coming off a 62-100 season, the Marlins have reworked their front office. Michael Hill was named president of baseball operations and Dan Jennings was promoted to GM. Dan Noffsinger was named director of baseball operations.
Joe Frisaro is a reporter for MLB.com. He writes a blog, called The Fish Pond. Follow him on Twitter @JoeFrisaro. This story was not subject to the approval of Major League Baseball or its clubs.