This year, the accounting firm faced another challenge - the introduction of online voting for the first time, alongside the option of traditional paper ballots mailed out to Academy members around the world.
More than 5,800 movie industry professionals who are members of the Academy of Motion Picture Arts and Sciences were invited to vote in 24 Oscar categories, starting on February 8 and ending at 5 pm PST on Tuesday (0100 GMT On Wednesday).
The results will be tabulated at a secret location by accounting firm PricewaterhouseCoopers, who deliver the envelopes with the winners' names from backstage at the February 24 Oscars ceremony, televised live from Hollywood.
With the races for Best Picture, Director, Actress and Supporting Actor considered too close to call by awards pundits, movie studios have been blasting newspapers, radio, trade publications and television with promotions for their nominees.
The Los Angeles Times estimated that Warner Bros., the studio behind "Argo," and Walt Disney Co, which is distributing "Lincoln," had spent about $10 million each in Oscar campaigns in recent weeks. The two movies are locked in a tight contest for the top Oscar prize - Best Picture.
PricewaterhouseCoopers say there has never been a security breach in the secret voting in the 79 years it has worked with the Academy on the balloting process.
This year, the accounting firm faced another challenge - the introduction of online voting for the first time, alongside the option of traditional paper ballots mailed out to Academy members around the world.
"It's a very robust system with a number of security features," Rick Rosas, who has worked on the Oscars with PricewaterhouseCoopers since 2001, told Reuters of the electronic method.
He said more than half of the Academy's members voted online.
The online system was hit by glitches and complaints from some of the Academy's members, most of whom are over 50 years old, when the system went live in December for Oscar nomination choices.
Some members reported problems with passwords and user names and voting for Oscar nominations was extended by 24 hours. The Academy later reported a high turnout of voters.
The move to electronic voting is aimed at speeding up the Academy Awards process, especially for members who work or live overseas.
Steven Spielberg's presidential drama "Lincoln" goes into Sunday's Oscar ceremony with a leading 12 nominations, including Best Picture, followed by "Life of Pi" with 11, musical "Les Miserables" and comedy "Silver Linings Playbook" with eight apiece, and Iran hostage thriller "Argo" with seven.