April may be the cruellest month, but September is the coolest for regional theatres. Playgoers from Penzance to Perth are currently studying their brochures and shuddering with anticipation. They might, indeed, fear the worst, as Groucho Marx did when contemplating Eugene O'Neill's next gloomy epic: "I feel a Strange Interlude coming on." However, grouchiness plays second fiddle to optimism at the moment, as the major regional houses - still buoyed by a £25m injection of extra funding from the Treasury two years ago - plan this crucial, risky period in the year's activity leading up to the economic lifebelt that is the Christmas panto.

The biggest beneficiaries of the funding hike in the north were the Liverpool Everyman and Playhouse, two theatres with contrasting histories that are now ruled by a single artistic management. Both theatres have had a rough ride over the past 15 years, losing status and national profile. But with Liverpool designated European Capital of Culture 2008 and the Everyman celebrating its 40th anniversary this month, it is high time the tide turned.

The Everyman and the Playhouse illustrate the contrasting - some would say conflicting - functions of the modern repertory theatre system, which is exactly 100 years old. The Abbey in Dublin opened in December 1904, and was soon followed by the Gaiety in Manchester (1908), the Glasgow Rep (1909), the Liverpool Playhouse (1911) and the Birmingham Rep (1913). The Everyman, which opened in 1964, was part of a second wave of rep theatre. It was specifically aimed at the student and Beatles-crazy Cavern Club crowd. In its glorious period of the early 1970s, the writers John McGrath, Willy Russell and Alan Bleasdale hit the stage, and the actors (in the company run by the director Alan Dossor) included Alison Steadman, Julie Walters, Jonathan Pryce, Antony Sher, Bill Nighy, Matthew Kelly and Pete Postlethwaite. New writing and "community" came to mean the Everyman, while the Playhouse atrophied to such an extent that Russell and Bleasdale switched sides in the mid-1980s to try to do something about it. They essentially failed, despite the 1986 premiere of Russell's Blood Brothers.

Later, Bill Kenwright came to the rescue of the Playhouse while the Everyman faced closure. Today, under the new artistic director, Gemma Bodinetz, there are signs of recovery. The combined average audience has improved from 46 per cent to 52 per cent (still poor) and the companies visiting the Playhouse - which is programmed with touring and shared productions - have done fairly well.

The challenge now for Bodinetz is to attract an audience for home-grown work. To this end, she is taking a huge risk and celebrating the Everyman's 40th with two brand-new plays by first-time authors. The Kindness of Strangers by Tony Green is a large-cast play about asylum-seekers in Liverpool ("The most brilliant play I've read for years," said Bleasdale), while Urban Legend by Laurence Wilson shows how men cope without women - or not - in Bootle.

Bodinetz says that she is "relighting a spark based on the heritage of the Everyman". However, she insists that she is looking to the future, not only in reanimating the Scouse appetite and talent for aggressive, funny new writing with a local flavour, but also in attracting international work. The Playhouse would be ideal for this, although the separate identities of the two houses are no longer an issue. In fact, the Everyman's anniversary is being honoured at the Playhouse with a new production of The Anniversary, Bill MacIlwraith's blackly hilarious 1966 "mother-in-law" comedy starring Sheila Hancock, which runs until 2 October.

Yet Liverpool will battle to find a balance between the home-grown and the out- of-town. The same is true even at the bigger, more stable regional theatres: the West Yorkshire Playhouse in Leeds, the Nottingham Playhouse and the Bristol Old Vic. Yet their health is crucial. Everyone knows that new talent comes not from the West End, or even the Fringe, but from these venues that feed into the monoliths of the National Theatre and Royal Shakespeare Company.

The best example of this is the work that has come from the five-year tenure of Michael Grandage at Sheffield Theatres - another, more glorified two-tier operation, between a classic Victorian touring house (the refurbished Lyceum) and an experimental venue (the Crucible). Grandage - who is also having success as artistic director of London's Donmar Warehouse - is moving on. His most important legacy is the creation of a new audience via a vibrant educational policy and the snaring of box-office hits such as Joseph Fiennes, Kenneth Branagh, Diana Rigg and Derek Jacobi, who stars in Friedrich Schiller's Don Carlos which opens on 22 September.

Bringing Sheila Hancock to Liverpool is a start, but what Bodinetz must do (helped by a £1.3m annual Arts Council grant for both theatres) is to tap once more the energy and creativity of locals both on stage and in the audience. Only then can Liverpool theatre regain a truly national voice.

Michael Coveney is a theatre critic and author