Trask had been CEO since 1997 and had been with the team since 1987, making her a pioneer for women in pro sports management.
"Having honored a commitment that I made to effectuate a smooth transition and transfer of control, I no longer wish to remain with the organization," Trask wrote in a statement provided the media.
"For over a quarter of a century, it was my honor and my privilege to work for the Raiders. I will forever appreciate the opportunity afforded me by Al Davis."
Davis died in 2011 and the team is now owned by his son, Mark.