A quick check on NRE Wakefield Kirkgate to Chapeltown is shown as Off Peak £7.60 return, that's even during the evening peak period.
I was under the impression the peak fares only applied if your start and finish points were in the same travel zone,(West York's, South York's, Greater Manchester, etc), but if you crossed into another zone it was still Off Peak.
I often travel from Huddersfield to Manchester during the so called peak period and only pay Off Peak fares, If I travelled to Leeds though I would have to pay for an Anytime Ticket.