The drama, which has been written by Prison Break creator Paul Scheuring, focuses on the editor of Modern Skeptics magazine.
Edwards has now signed up to play the journalist, Hank Foley, Deadline reports.
Hank finds himself being drawn into a massive conspiracy when his wife is kidnapped.
As well as starring as Dr Mark Greene in ER, Edwards appeared in Northern Exposure and had parts in movies such as Zodiac and Top Gun.
Carmen Ejogo has also signed up for a role in Zero Hour, Deadline says.
She will play the FBI agent investigating the kidnapping of Hank's wife, but she may have hidden motivations of her own.
Ejogo previously starred in the shows Kidnapped and Chaos and had a role in the movie Away We Go.
The duo join Addison Timlin, who has already joined the cast of Zero Hour and will play a journalist working for Modern Skeptics.