The 29-year-old Tocumwal Golf Club trainee made birdie on the first playoff hole at Keysborough to beat nine other players to secure one of four spots on offer at the largest Australian Masters prequalifying field in years.
He nailed his second shot to within eight feet on the par-4 tenth to book a tee time alongside world number one Tiger Woods after finishing with a four under 69.
Not so lucky was his work colleague and fellow trainee Matthew Docking who recorded a bogey on the last hole of his round to force the playoff.
But Tocumwal is well represented with Rodney Booth another confirmed starter.
Competing in this year's JBWere Masters has fulfilled a lifelong dream for McKay.
"I'm just like any golfer, you can only dream about playing in the same field as Tiger Woods," he said.
"It's the first time I've tried to get into any of the big tournaments in Australia.
"I reckon I've got into the best one in years. I'm still pinching myself that I'll be there with thousands of people looking at me."
McKay, who has his boss and coach Michael MacGregor on the bag, hasn't got any huge expectations for the week ahead.
Although he admits, making the half way cut is something he's shooting for.
"If I'm there on the weekend then I'd have done pretty well.
"To be honest I didn't think I'd get one of the four spots from the 100 plus professionals.
"Most of those guys are a lot more experienced than me. I'm surprised I was the only person to make birdie in the playoff.
"It was a real shock when they told me I'd be playing in the Australian Masters."
New Zealand's Brett Holloway had the day's best score with a 67 at Keysborough.
Victorian Michael Choi and Kurt Carlson from Queensland took the other two positions with a 68.
More than 100 professionals teed up this year, with many making the trip down from Queensland after the Cellarbrations Queensland PGA in Toowoomba.
Meanwhile, former WA PGA champion Andrew Pitt got his JBWere Masters campaign off to a stellar start.
The talented Victorian won the Yarrambat Golf Course pro-am, holding off a solid field of professionals with a four under 67.
At least five players used the event as a warm up for Kingston Heath where more than 100,000 people are expected through the gate over the four days of competition.
Want video tips delivered straight to your inbox? Subscribe to iseekgolf.com newsletters.