The 45-year-old spent six years at the club as an assistant under Leigh Matthews, a term that saw the club win three consecutive premierships and be hailed as the greatest team of the modern era, before heading to Essendon, where he played almost 250 matches.
O'Donnell said the decision to leave the Bombers was a mutual one between him and the club.
"I'd been there six years, I'd been under two senior coaches. I think I'd had my time as an assistant there," he said on SEN.
New Essendon coach James Hird had put a broom through Windy Hill, O'Donnell said, "and good luck to James, too.
"Success has followed him and hopefully it keeps doing that and the club can turn things around from the last year."
O'Donnell welcomed the opportunity to work with Michael Voss.
"The club has, from afar, been in a little bit of turmoil but with new people coming into the club and the environment that Vossy's trying to create to get the best out of his playing group, it all looks onwards and upwards for the club.
"I'll come with no agendas, I'm true to the senior coach, I'm backing his philosophy and helping him be a better coach as well, and hopefully getting the best out of the playing group."
O'Donnell played 243 games for Essendon between 1987 and 1998 after a 67-game apprenticeship in the reserves.
Along the way he spent two years as captain, played in the 1993 premiership side - the same year in which he won the club's best-and-fairest award - and played for Victoria nine times.
After finishing his playing career, O'Donnell moved to the Lions before returning to Windy Hill as an assistant to Kevin Sheedy and later Matthew Knights.
