The decision to name Peterman the starter was expected after he completed 33 of 41 passes this preseason for 431 yards, three touchdowns and one interception.
"Nate has earned the right," Bills coach Sean McDermott told reporters. "I thought his total body of work, all the way back from the spring through the summer and fall camp to this point -- he has certainly earned the right."
Peterman and rookie quarterback Josh Allen were among a large group of core players the Bills held out of Thursday's preseason finale, suggesting they were being considered for the starting job in Week 1. However, McDermott said after the game that AJ McCarron, who started and played the entire contest, was still in the mix to start the opener.
McCarron was then traded to the Raiders on Saturday.
By going with Peterman, the Bills avoid starting Allen against a defense known to dominate young quarterbacks. The Ravens are 14-2 (.875) against rookie QBs at home. Under coach John Harbaugh, Baltimore has allowed four touchdowns to rookie QBs at M&T Bank Stadium while forcing 13 interceptions in 10 games.
Peterman will be the Bills' 11th season-opening starting quarterback since 1997, their first season without Jim Kelly. The only teams with more season-opening starting QBs over that span are the Cleveland Browns (16), Washington Redskins (12) and Minnesota Vikings (12). The Arizona Cardinals and Tampa Bay Buccaneers also have had 11 over that span (including this season).
After McCarron suffered a shoulder injury while starting the second preseason game, Peterman and Allen split snaps with the first-team offense. Allen started the Bills' third preseason game in an effort by McDermott to give the No. 7 overall pick some experience in that role. Allen completed 6 of 12 passes for 34 yards and was sacked five times.
"Josh is on schedule," McDermott said. "I've been very pleased with the way he's developed to this point in time. Listen, you learn a lot from the first game of the regular season, whether you're playing or not playing, when it's your first time. I can just go back to my first time and being a part of the first game in my career. You learn an awful lot. But that being said, I expect that Josh will be ready to go when his number is called, whenever it is called. That's his focus right now."
Allen told reporters that he doesn't consider this "a step back, and ultimately it's gonna help me in my progression."
McDermott and general manager Brandon Beane have lauded Peterman for his attitude and approach since he threw five interceptions in his NFL starting debut last November against the Los Angeles Chargers. McDermott, who benched Tyrod Taylor in favor of Peterman for that game, turned back to Taylor for the second half and the remainder of the season. The Bills traded Taylor to the Browns this offseason.
"I believe [Peterman] is a resilient young man," McDermott said. "He's certainly come through some times of adversity throughout his career. He's still a young player. I've been impressed with his mental toughness, his command of the offense. The way he's generated yards and then points in the preseason, as well. The way he's developed to this point. Let's keep in mind he's a young player."
Three weeks after his disastrous starting debut, Peterman made his second career start last December in a snowstorm against the Indianapolis Colts. He completed 5 of 10 passes for 57 yards and a touchdown in that game, a Buffalo win, before exiting with a concussion.
"I understand what happened [last November against the Chargers]," McDermott said in June. "I acknowledge that. But that doesn't define someone. One game never defines someone. The guy is a winner. You hope over the course of time that will come out, but his whole approach ... is what you want."
Peterman, 24, was a fifth-round pick by the Bills in the 2017 draft. He began his college career at Tennessee before transferring to Pittsburgh for his final two seasons.
Peterman said he was "excited" and "very thankful" to be named the starter.
"It's a great opportunity. [I] definitely worked really hard to try and get myself in this position and I think a lot of work is still in front of me. We've got a big challenge in front of us this week, and that's what I'm focused on," he said.
ESPN's Jamison Hensley and ESPN Stats & Information contributed to this report.