These were iconic QBs in program history he eclipsed: Bradlee Van Pelt, Caleb Hanie, Moses Moreno, Terry Nugent and finally, last weekend against Utah State, Kelly Stouffer, who held the all-time yards passing record for nearly three decades until Grayson came along.
This from a quarterback who didn't really know how to dissect a defense until he learned from coach Jim McElwain. This from a QB who broke his collarbone twice - once in a game and another while moving a couch - and who heard plenty of boos early in his career for errant passes.
''This record is a huge honor. An unreal feeling,'' said Grayson, whose Rams (6-1, 2-1 Mountain West) host Wyoming (3-4, 1-2) on Saturday. ''Bradlee Van Pelt is still the man around here, in Fort Collins, so even to be mentioned with him in the same sentence is a huge honor.''
To think, the senior from Vancouver, Washington, almost wound up at Louisville. But the coach there at the time, Steve Kragthorpe, already had two other highly touted QBs. He placed a call on behalf of Grayson to good friend and then-CSU coach Steve Fairchild, a standout QB for the Rams in his own right.
Fairchild was sold on the 6-foot-2 Grayson and he ended up starting three games for Fairchild in 2011. Then, the coach was let go.
Enter McElwain, the offensive coordinator at Alabama who worked with QBs Greg McElroy and AJ McCarron as the Tide captured two national titles.
McElwain was a film guru. Grayson? Not so much.
''I just went out and threw the ball,'' said Grayson, who's thrown for 7,250 yards in his career, toppling the mark of Stouffer (7,142), the QB from 1984-86. ''If somebody was open, they were open. If they weren't, they weren't. That's why I threw the amount of interceptions that I did, and the incomplete passes.''
The boos from the fans followed - and the obvious question: Could he be the quarterback McElwain needed to turn around the program?
McElwain had faith.
Grayson began making strides his sophomore season, but then he broke his collarbone against Air Force. He returned, but took a backseat to another quarterback.
''That was the first time I'd ever been injured and it was hard to handle,'' said Grayson, who also broke his collarbone lifting a couch last April. ''That was the real low point for me.''
With his spare time, Grayson studied film with McElwain, learning what to do when a defense presented a particular look.
''I'm night and day from what I was early on in my career,'' Grayson said.
He set a school record last season in yards (3,696) and tied another mark for TD passes (23) as the Rams went to their first bowl game since 2008. They beat Washington State 48-45 in the New Mexico Bowl, with Grayson helping lead the comeback.
The Rams are already bowl eligible this season and have a good shot at something even bigger - winning the Mountain Division of the Mountain West Conference. They trail Boise State, a team that beat them earlier this season.
''This is the most confidence our team has had since I've been here,'' Grayson said.
McElwain has certainly noticed the soaring confidence of Grayson.
''He has become a much better student of the game,'' McElwain said. ''Our offense is fairly complex when it comes to that position, as he found out early in his career.
''He's definitely playing faster I think because of his understanding.''
This helped, too - attending the football camp of his boyhood idol, Peyton Manning. He and the other college football players got to spend about an hour with Manning and his brother, Eli, one day, asking anything on their mind.
Grayson just listened.
''He told us about dummy cadence. How he gets defenses to show their key,'' Grayson said. ''You always hear he is a perfectionist. To be able to see it and witness that was very special to me.''
Like Manning, Grayson's setting plenty of records these days.
Next up for Grayson: the school's career TD record.
He's four away from breaking the mark held by Moreno (51). Grayson's also closing in on the all-time completions record, just nine away from surpassing Stouffer (577).
Not that Grayson's even thinking about those marks.
''Just go out and play,'' Grayson said. ''Because once you get too concerned with records, it seems to take you out of your game.''
AP freelance writer Dale Bublitz contributed.