McCall fired a seven under par 65 to claim the outright lead in the clubhouse at a 10 under par total.
Toomey, who shared the round one lead, responded and made a great birdie at the last for a four under par 68 to also post that number.
McCall has shot rounds of 73, 68 and 65 at Bridge Pa this week and is feeling more comfortable after a change in game plan.
"I hit the ball really well and I was always in play and it was one of those days where everything was on form," the 20-year-old said.
Toomey is just enjoying the occasion of being in contention at the New Zealand Stroke Play.
"I was a little more nervous," the 18-year-old said.
"It is a little bit different when the draw gets seeded but I am absolutely stoked to get through with four under and put myself in a good position."
Overnight joint leader Hamilton's Matthew Perry went the other way in round three with a one over par 73, dropping him back to a share of third place with Nicolas Coxon, three shots back from the leaders.
"It was a little bit frustrating," the 24-year-old from the Hamilton Golf Club said.
"The course is there to be had - there have been a couple of great scores out there - put one of those next to my name and we'll be right."
Fraser Wilkin (Royal Auckland) had a three under par 69 in the third round to climb into fifth place while former Hastings local Daniel Pearce is in sixth after an even par 72.