Known as Mr Edinburgh for the number of shows he's appeared in during the Fringe, the veteran comedian has seen many comics come and go over the years.

However, as he prepares to perform at The Stand tonight, as part of a bill full of younger, slightly more energetic stand-ups, is the flame-haired funnyman from the Emerald Isle bovvered about being superseded by the younger generation?

"Well, there's certainly a lot more comedians around now than there ever was," says O'Neill, who has been telling jokes professionally since 1985.

"Comedians today are a lot slicker. They seem to have their career path sorted well in advance. You know, do the tour, a bit of TV, diddley dah, etc. Back in my day, you just went up there and did it."

And he did. Practically an annual fixture at the Fringe, when it comes to good quality and good reviews, there are few comedians as consistent as O'Neill.

A prolific writer as well as a talented actor and poet, as the Irishman says, it's not that he prefers stand-up to anything else, it just depends on what ideas he has at the time.

"It's all about ideas," he agrees. "I am interested in all genres. If I was just a stand-up comedian then I might find myself going very hungry very quickly. I have to engineer my own ideas, and if that particular idea suits a film, a play or a poem, then I go with that. It all depends on the story and which genre I can best fit it into."

Over the past ten years O'Neill – who has won two Fringe Firsts, the Edinburgh Critics and LWT Writers' award for Best Comedy – has written so many one-man shows that he has trouble remembering how many he's performed.

However, fans of the Tyrone-born comic may be in for a bit of a shock when they discover his upcoming Fringe show Absolution is far removed from the comedy shows for which he's known.

"It's about a guy who kills paedophile priests," he deadpans, "the psychological journey of a man who, because of a horrific experience he had as a child in a small town, goes on to start killing priests."

Listening to O'Neill talk, it's not clear if he's joking or not – his debut film, Arise And Go Now, was a black comedy about priests and the IRA after all. Surely he's just having a laugh. Right?

"I suppose every dark drama has elements of comedy in it, but this is a genuinely dark piece, and it's unlike anything I've ever done, in that I'm being directed this time, by Rachel O'Riordan who directed Alex Higgins' Fringe biopic, Hurricane.

"I think it's my tenth one-man show, I can't be sure, but this is a complete change for me. Totally alien. Foreign you could say." Controversial drama aimed to shock is something you can guarantee every August during the Fringe. Yet, while sinister productions may be relatively new to O'Neill, Edinburgh and his love-hate relationship with the Capital, is about as old as Arthur's Seat.

"Every year I complain about the Festival. It's madness. Any sane person could tell you that. If you were to pick up the brochure and see just how many shows there is you'd say it was nuts. There's simply not enough of an audience any more. Yet every year I get drawn back to the place, like people who are drawn to the coast. It's impossible to make any money."

Strange. For a man with a reputable CV and umpteen awards occupying his mantelpiece at home, surely a successful performer such as O'Neill has a few bob in the bank?

"You have to remember my material will never appeal to a mass audience. It's suited to theatres with 200-300 people in them; it requires that sort of intimacy. So there's not a lot of money to be made from it. I performed to 600 people in Dublin, once, but it felt very compact. I doubt you'll see me in theatres that hold crowds of 1000."

And more's the pity. Undeniably talented and priding himself on continually coming up with new material, unlike other comedians who regurgitate the same old lines, O'Neill is always looking ahead to the next joke.

"I probably shouldn't say this," admits O'Neill, "but I've got 20 minutes of new material to try out during my Edinburgh gig. People might recognise little bits of it, but it's mainly all new, it just needs a bit of fine tuning. It'll be autobiographical, as most of my material is, but then all good comedy has an element of truth in it."

Finally, as a guy who regularly obsessed about the Rolling Stones in his stand-up shows (his fixation with them nearly cost O'Neill his marriage), what does O'Neill think about the grizzled old rockers today?

"I still love the Stones but I can't see them touring anymore. I saw Keith Richards playing with them last year and he looked like he was at the end of his tether. But then they keep coming back for more. Just like myself, they just get up there and do it."

• Owen O'Neill plus guests, The Stand, York Place, tonight and tomorrow, 9pm, £9 (£8/£5) tonight, £12 tomorrow, 0131–558 7272