The 28-year-old Haddington-based player sits joint-second, two shots behind leader Lucas Herbert, at the halfway stage at the Kilkenny venue after opening rounds of 66 and 67 for an 11-under-par total.
It’s the second time that Forrest has been in contention in the event, having played with Rock as he shot a 60 in the third round at Lahinch two years ago then with Rahm as he closed with a 62 to land the prize for the second time in three years.
“I can't wait,” said Forrest, who finished 14th on that occasion, of being back in the mix. “It's been a while.
“I've got great memories from the Irish Open at Lahinch two years ago playing with Rocky when he shot 60 on Saturday, and then played with Jon on the final day when he shot a low one to win. Won't be quite as mental as that, but I'm looking forward to it.”
Forrest carded an eagle and five birdies in his second circuit to sit as the closest challenger to Australian Herbert along with Englishman Dale Whitnell.
“Yeah, delighted,” said the Scot of his day’s work. “It's always tough to follow up a pretty good first round. I stayed really patient out there and probably wasn't quite as good off the tee today. So I had to work a little bit harder for the score.”
Richie Ramsay, who finished joint-second to Rahm at Portstewart in 2017, is also in the hunt after adding a 69 to his opening 67.
“I always think I play my best golf in Ireland,” said the three-time European Tour winner. “I won the Irish Stroke Play when I was younger.
“We (Scotland) won the under-21 team championships at the Island, just outside Portmarnock, and then I had a chance and played great at Portstewart. I kind of come here and I feel sort of at peace.”
While Herbert could be tough to catch, 2016 winner Rory McIlroy Open champion Shane Lowry and are hoping to give the home fans something to cheer about over the final 36 holes.
“I don't think I'm right back in contention, but I'm pretty close,” said McIlroy after leaping up the leaderboard on the back of a bogey-free 67 to sit alongside Lowry (69) on five-under.
“There's a lot of people between me and the lead, so I need to go out there tomorrow and shoot something probably a little better than I did today to give myself a real chance on Sunday.”
Lowry, who grew up just 90 minutes away, was outside the cut mark before digging deep to pick up three birdies in the last six holes.
“Pretty happy,” he said. “It's no fun at all playing golf on the cut mark, especially in your home tournament where you're trying to play good golf for them as well as myself.”
David Law covered his last 11 holes in five-under for a 66 to also sit on five-under, with Connor Syme on four-under and Marc Warren and Scott Jamieson also progressing on three-under.