The group is set to close the mill at Barry Docks by the end of October, bringing to a close a long history in South Wales. Consultations with the employees in Barry will begin over the coming days.
Its Atlantic Mills site was built in 1904 by the then Hovis-Bread Flour Company - Britain's largest flour miller, which has since been renamed Rank Hovis.
Premier said the closure would be phased over the coming months, impacting the mill's workforce and a number of local contractors. It follows the closure of its Glasgow mill in early April, which impacted 15 employees.
The latest blow comes as part of a shake-up of its Rank Hovis network, which has a history dating back some 138 years.
Premier will split the milling business in two, with mills in Southampton, Manchester and Newbridge to be focused on producing flour for supermarkets and other food manufacturers, trading under the Rank Hovis brand, while the remaining mills in Wellingborough, Selby, Andover and Gainsborough will supply flour for the company's baking and grocery business.
Bob Spooner, managing director of Premier Foods' bread division and group supply chain director, said: "We recognise the impact this proposal will have for our employees in Barry and we thank them for their contribution over the years. However, it's not possible to continue on the current path given excess capacity in the marketplace."
Premier said it would inject an extra £1 million into its Southampton and Wellingborough sites to boost production at the mills. It has been overhauling its bread division, recently announcing the closure of three bakeries in Eastleigh, Greenford in west London and Birmingham, while also shutting distribution centres in Greenford, Birmingham, Mendlesham and Plymouth with the loss of around 900 jobs.
The wider Premier business, which is struggling under a near £1 billion debt mountain, hopes to save around another £20 million this year through the bread business restructure and general cost cutting. Rank Hovis traces its roots back to 1875, when Joseph Rank saw the potential of grinding wheat with steel rollers in preference to millstones. It was bought by Premier Foods in 2007.