Oldcorn, still searching for his maiden Senior Tour title after recording his second runner-up finish at last week's ISPS Handa Senior Masters, signed for a best-of-the-day 66 to move to five under par, one stroke clear of England's Barry Lane.
The 51-year-old from Edinburgh has finished inside the top 12 in all four of his appearances on the regular 2011 Senior Tour Schedule, but labelled his display in Hexham yesterday the best of the current campaign.
"I just got into the zone today, and felt like I could birdie even the hard holes," said Oldcorn. "I've been playing well now for two or three weeks."
Despite bogeying his last two holes, Briggs joined Oldcorn on five-under. "I'm as surprised as anyone to be leading the tournament," he said.
After carding rounds of 71, Scottish pair Gordon Brand Jnr and Sandy Lyle share ninth place on one under.