Three-time Senior major winner Montgomerie, who had started the day just two shots behind the German pacesetter, dropped three shots in the final three holes as he signed for a second-round 76 to sit on five-over.
Langer leads on one-over along with former Open champion Tom Lehman, as well two other Americans in Billy Mayfair and Steve Flesch plus Argentina’s Mauricio Molina.
Lehman, the Claret Jug winner in 1996, carded a one-over-par 72, birdieing the last to join Langer in a share of the clubhouse lead just moments after the nine-time Senior major winner also made a gain on the 18th to sign for a three-over 74.
“I was hitting it solid, that’s the big thing,” said Lehman. “I was hitting it in the middle of the club face most of the time and able to control the ball. I think the first eight holes were horrific, playing in the worst conditions ever, I think.
“To get off the front nine level par, it was one of the better nine holes I’ve ever played.”
Langer, a 13-shot winner at the same venue in 2014, said of his effort: “It was actually much harder this morning, but I’m right in the mix. There’s a lot of golf to be played.”