The operator, which runs rail services across eastern England and into London, said the changes “reflect more people heading back to work and school”.
But it said commuting levels may take a while to recover from the pandemic.
A spokesman said it probably “would not see the same number of people doing the five-day-a-week commute”.
Head of corporate affairs, Jonathan Denby, said there might be new customers, as many people “previously really only had one option which was either to commute and do five days or not travel at all”.
“Actually when they suddenly have the option of just doing two or three days that might open up a new market,” he said.
Greater Anglia runs rail services into London Liverpool Street from Essex, Suffolk, Norfolk, and parts of Hertfordshire and Cambridgeshire,
A full timetable has been reintroduced on Great Eastern services from Ipswich, Harwich, Clacton, Colchester, Braintree, Chelmsford, Southminster and Southend.
Additional Intercity services have been introduced to Norwich, Diss, Stowmarket, Ipswich, Manningtree, Colchester, Chelmsford, Stratford routes to London, and on West Anglia services between Kings Lynn, Cambridge, Hertford East and London.
The company said it meant these routes had a “now a near normal service for most of the day”.