Having never acted on the small screen before, the 32-year-old has just been chosen for the lead role in ITV's new police drama Single Handed and the newcomer couldn't be happier.
"There's something really complex about the series and I was delighted to get it. As a first job on telly, it's not bad," he gushes.
Set in Connemara in the West of Ireland, McDonnell plays Police Sergeant Jack Driscoll. McDonnell explains: "What's interesting about Single Handed is that it's not a straight-forward whodunit? It goes into my character's personal life and he doesn't just focus on solving crimes. It deals with his relationship with his father, who had the job before him. It also shows how he's craving for the normal things in life, like a girlfriend."
McDonnell is also keen to point out that while there may be plenty of other police dramas out there, none are quite like this: "When I first read the script, it didn't seem like other police dramas. I think it's more like a contemporary take on a Western, which was interesting to me. He's driving around hundreds of miles in the middle of nowhere."
"In Ireland we haven't really done police dramas before. You get rural and grisly dramas but the two aren't often mixed together. It has this interesting feel to it and it lulls you into a false sense of security. You think you're going to watch this knockabout Irish drama and then suddenly you'll realise it's a really dark piece."
With no experience of either life in the force or living in the countryside, McDonnell had to quickly gain some insider knowledge. He spoke to a police consultant and once out on set "talked to a lot of local cops who came to stop traffic for us".
While McDonnell may lack TV experience, his enthusiasm makes up for it. For many years he has honed his acting skills in theatre but had almost resigned himself to never getting to perform on the small screen.
"I was rubbish at doing auditions for TV shows. As soon as you put a camera up in the room I went to pieces", he admits.
For Single Handed, his nerves weren't helped when he saw what the role would involve.
"I'm not a good driver and the first shot in the programme is me in my 4x4, so that wasn't good. I just had to go for it and be thrown in at the deep end, there was no time to stop and think about what was happening. But if I made a mess of it, it was terrible for everyone. Luckily, I knew a lot of the cast already so that made it easier."
McDonnell talks fondly of the camaraderie between the Irish acting fraternity.
"It's a small world over here and so the actors tend to do television, theatre and films. So on this drama, I knew quite a lot of the cast.
"I hadn't met the actors playing my parents, but two of the lads who I'd been acting in a play with before we started filming Single Handed were also in the show. The three of us all went on the train together to the auditions, so that was great - not having to go on to another job on my own. They've given me great support."
McDonnell also has support in the form of his girlfriend Jill, who he lives with in London's Stoke Newington. While he spends much of his life out on the road, travelling from theatre to theatre, Jill works in corporate finance. In McDonnell's case it seems distance really does make the heart grow fonder.
"I think it might be hard for Jill sometimes because I might be away for two months at a time. Over the years though we've figured it out. I saw a Helen Mirren interview recently and she said her husband doesn't travel with his work and she's away all the time, so they're always happy to see each other.
"It's true, we're always happy to see each other and now I try not to go away as much as I did previously. We muddle along!"
However, living in London does mean the proud Irishman does miss out on seeing his family, as his two sisters and one brother, all live near Galway. If McDonnell hadn't decided to take the plunge and move to London, he says it's likely he'd still be in the area.
It was only when he was at university in Galway studying English and History that the acting bug took hold, so he packed up his possessions and headed for England, where he took an acting course in London.
His hard work over the past 10 years means he has been kept busy with theatre productions and now of course, Single Handed.
But there have been times when he's considered giving it all up.
"I had a year where I didn't work at all. I thought about quitting then, I was thinking that instead I would buy a pub. I was seriously considering it when luckily I got an acting job at the Royal Court."
Now McDonnell is happy to stay in acting but admits he doesn't think in the future he'll be able to go back to theatre roles full time.
"My long-term aspirations are three-fold: To be healthy, happy and, if we have kids, to give them everything they want. That probably means TV and film work because I wouldn't be able to do that on a theatre wage. If I can continue to do decent work and work that interests me, I'll be happy."
Extra time - Owen McDonnell
The only link to showbusiness in McDonnell's family is his granny who used to be involved in "the local variety society"
Once he had graduated from acting school, McDonnell gave himself five years to make a living out of acting, which he achieved
McDonnell is currently learning French for a film which starts in April
Prior to the role in Single Handed McDonnell was performing in The Lieutenant Of Inishmore
He is also set for a role in the new TV film Wild Decembers