JJ Abrams is hosting it and Colin Farrell's up for an award – welcome to what Steven Spielberg calls the best party in LA

When Jason O'Mara moved to Hollywood, an unknown actor with a Dublin brogue, it would have been useful to plug into the Irish network – except there wasn't one. "When I first got here, I wasn't aware of any Irish community that I should be part of."

Little harm it did him. A decade later O'Mara is a familiar face, thanks to network dramas such as Vegas, Justice, Life On Mars and Terra Nova. All the characters were American and the actor worked hard with a dialogue coach to erase unwanted lilts.

But this Thursday, days before the Oscars, O'Mara and hundreds of compatriots will gather to celebrate Irish success, and belated networking, at an annual pre-Oscar hoolie that Steven Spielberg has called one of the best parties in LA. The Oscar Wilde: Honouring the Irish in Film event will present awards to Colin Farrell, the Oscar-winning makeup artist Michele Burke and Lionsgate vice chairman Michael Burns to show the industry that the Irish have arrived in force. The producer-director JJ Abrams, better known for blockbusters than his affinity for Ireland, will host the bash for the second consecutive time at his Bad Robot production company in Santa Monica.

"When you get out to LA you realise there's a huge amount of Irish people living there – writers, actors, technicians, you name it," says Cecelia Ahern, whose novel PS I Love You was made into a film starring Hilary Swank. Lionsgate is currently turning another of her novels, Where Rainbows End, into a movie under the name Love, Rosie.

Ahern is based in Dublin, but regularly visits LA to keep projects ticking over. "I love going over. It's such a powerful place to get things done." The annual Oscar Wilde shindig, she said, nurtures bonds between the transplanted Irish. "It's really good fun and puts everyone in the same room."

Stars such as Pierce Brosnan, Liam Neeson, Gabriel Byrne – followed more recently by Farrell, Cillian Murphy and Michael Fassbender – have long given an Irish glint to Tinseltown, but the growing band of actors, technicians, executives and producers behind them is now making its presence felt. They have arrived without "the British are coming" fanfare which greets any putative British breakthrough; perhaps a good thing given the jinx that can punish such hubris. Some have been here for decades, others are fresh out of LAX, blinking in the Californian sunshine; but what's new is the improved cohesion.

"There is a sense of community," said Peter Devlin, who started as a sound audio assistant with the BBC in Belfast and is now a veteran, Oscar-nominated sound mixer who has worked on Transformers, Star Trek and Pearl Harbor.

"A boom operator will tell me about something Catherine George (a costume designer, sister of director Terry) is working on, or a project with Andrew Ward (an assistant director) or Kevin Hannigan (special effects). We keep running into each other." Devlin lives down the road from David MacMillan, an Irish-born sound engineer who has won three Oscars.

Irish accents were sufficiently exotic in 1992 for Marlon Brando to approach Devlin on the set of Christopher Columbus: The Discovery, and ask if he was from Belfast. These days Irish brogues are much more common – at least behind the camera. "There's a genuine soft spot that Hollywood has for Irish talent, but you'll still only get work if you can sound American," said O'Mara, who can switch from Brooklyn to New Jersey cadence.

"There's a preconceived notion about the Irish. People assume you like a good time, have a sense of humour and you're tough, fighting and drinking and all that. When going for a role that can work for or against you." A former rugby player, O'Mara does many of his own stunts.

The Yank in Ireland exploring ancestral roots is a Hollywood trope since John Wayne's The Quiet Man in 1952, but the traffic is increasingly in the other direction. Laura Livingstone, from Armagh, moved to California in 2007 and has done special effects for Iron Man 2, Looper and A Good Day to Die Hard. "We're getting more recognition. I think we're making more of a splash." Bad Robot, one of Hollywood's hottest outfits even before Abrams was tapped to direct the next Star Wars film, hired Livingstone after hosting last year's party.

The advent of social media, especially useful in a city as disparate as LA, accounts for some of the improved Irish networking. Trina Vargo, founder and president of the non-profit US-Ireland Alliance, accounts for the rest. A one-woman dynamo who worked with the late Senator Edward Kennedy in the 1990s Northern Ireland peace process, she created a scholarship scheme for Americans to study in Ireland while simultaneously working the Irish angle in Hollywood, a task aided by a longtime friendship with Katie McGrath, Abrams's wife.

Vargo has accused Irish officials in the past of missing chances to woo studios and bring productions to Ireland, and of skimping on funding for the Oscar Wilde event, now in its seventh year, forcing her to scramble for corporate sponsorship elsewhere. However, she said talks this week with the heads of the Irish Film Board, who are visiting LA, left her hopeful that greater official commitment and tax breaks may generate opportunities to "match the island's creative talent".

One of the reasons Spielberg turned up last year was the party's reputation for craic – unlike the plethora of formal, rictus-smile events around Oscar week that many feel obliged to attend. There is live music, whiskey and jokey ceremonies where non-Celts such as Abrams and Michelle Williams are declared honorary Irish. Speeches by Kenneth Branagh and the screenwriter John Logan brought the house down last year.

The makeup designer Michele Burke, one of tonight's guests of honour, said it was gratifying to see the Irish band together given their otherwise "fierce individualism" and traditional lack of networking. "It's in our DNA to be self-reliant." Now feted for her work in Bram Stoker's Dracula, Mission Impossible and Cyrano de Bergerac, it was not thus in 1983 when Burke won her first Oscar for Quest of Fire. Based then in Toronto, she missed the ceremony and collected the statuette with her sister from the post office.

"It was in a box and was so heavy they thought it was hash or something. When they took it out my sister told them to present it to me. They did, and people clapped."