The drama, which stars Hermione Norris and Ugly Betty actor Eric Mabius launched last week with 4.4m viewers. However, a declining audience over the first four episodes saw it attract an audience of just 2.9m on Monday and 2.6m last night.
BBC drama controller Ben Stephenson told The Guardian that the schedule change does not mean that the broadcaster will not take risks.
"BBC1 and BBC Drama support creative risk," he said. "Sometimes this means that talented people make shows that don't engage enough of the audience. I have so much respect for any writer who has the nerve and confidence to create their own original world and serve it up to an audience."
He added: "It's highly important to me to support them no matter how the project is received, whilst primarily always trying to engage the widest possible audience."
The eight-part series, filmed on location in South Africa, was made by Kudos who have been behind BBC hits including Spooks and Hustle.
Outcasts will move to its new Sunday night slot on BBC One on February 27.
> 'Outcasts' exec 'has planned second run'