The pair had been assured of places on the club's rookie list and were part of the group to re-join Bombers training this week.
Steinberg, who was a second-round NAB AFL Draft pick in 2010, has not made his senior debut in three years with the club.
He showed improved form at the end of the season at VFL level as a medium defender after coming to the club as a forward.
Dell'Olio will spend his third year on the rookie list after playing 11 games in his first two seasons with the Bombers.
"The re-signing of Cory and Ariel fills two of the available four rookie positions on our list for the 2014 season," list manager Adrian Dodoro told essendonfc.com.au.
"It takes a resilient character to stay on the rookie list at a club and I think that is a great asset that both of these players possess."
Lauchlan Dalgleish, who was a rookie last season with the Bombers, was recently elevated to the club's senior list for 2014.
