The former Cambridge midfielder headed home Conor Hourihane's corner in the 95th minute to rescue a point against the Posh.
"I'm delighted with my first league goal," Berry told the press after the game. "It's always pleasing to get that. I thought we deserved the draw or maybe even a win.
"It was a good performance from everyone but we just lacked that cutting edge."
Berry did score his first Barnsley goal against Oldham in the Johnstone's Paint Trophy last October, but his first league goal arrived in a man-of-the-match display for the 22-year-old at the weekend.
"It's been a bit long, I would have wanted to get it (the goal) earlier," he continued. "But I'm just pleased.
"The boys have been playing well and it's been hard to get into the team. I've had to put extra work in on the training ground to keep fit. It's finally paid off."
