After attending Littleton High School, he enrolled at Abilene Christian University without a scholarship. He was redshirted in his freshman year. In 1973 as a junior, he led the nation's small colleges in passing and total offense, completing 195 of 360 passes for 3,167 yards and 28 touchdowns, while rushing for 251 yards. He set a school record by passing for 434 yards and 4 touchdowns in a 41-7 victory against Southwest Texas State University. Longley finished the year guiding his team to 11 straight victories and the NAIA championship. He also received Small College All-American honors and was named, along with teammate Wilbert Montgomery, to the 1973 NAIA football All Star team, whose backfield included Walter Payton. He forwent his senior season to declare for the NFL draft.
As a result of leaving college with eligibility still remaining to be completed, he entered the supplemental draft in 1974, where he was selected by the Cincinnati Bengals. On July 3, he was traded to the Dallas Cowboys in exchange for a fifth round draft choice. He was named the backup quarterback to Roger Staubach, after having a strong training camp and Craig Morton being traded to the New York Giants. He is best remembered for his performance in a Thanksgiving Day game in 1974 against the Washington Redskins. Longley, then a rookie, came into the game for an injured Roger Staubach with the Cowboys trailing 16-3 in the third quarter, and facing elimination from the playoffs. After hitting Billy Joe Dupree for a 35-yard touchdown pass, he led the Cowboys on a 70-yard drive capped by a 1-yard Walt Garrison touchdown run. Finally, with the Cowboys behind 23-17 and with only 28 seconds left with no time outs, Longley hit Drew Pearson down the middle for a 50-yard hail mary pass touchdown which gave the Cowboys a dramatic 24-23 come from behind victory. Because Longley had no expectation of playing in that game and was completely unprepared, Cowboys lineman Blaine Nye sarcastically called his winning effort "the triumph of the uncluttered mind." The game was named the second-best in the history of Texas Stadium by ESPN in 2008. In 1975, he started in the season finale against the New York Jets, so Staubach could rest for the playoffs. He brought back the team from a 0-14 deficit to win 31–21. On August 30, 1976, after a training room incident in which he sucker-punched Roger Staubach during the 1976 preseason, the team suspended and eventually traded him to the San Diego Chargers along with a first round draft pick, in exchange for a first and second draft choice. The Cowboys used those two picks and two other picks to eventually land the No. 2 overall pick in the 1977 draft, selecting Tony Dorsett.
San Diego Chargers
In 1976, the San Diego Chargers acquired him with the intention of creating a competition with Dan Fouts. He appeared in 3 games, completing 12-for-24 for 130 yards along with 2 touchdowns and three interceptions while being sacked seven times. He was released on September 8, 1977.
Toronto Argonauts (CFL)
On September 22, 1977, he was signed by the Toronto Argonauts of the Canadian Football League. He played in 8 games before being released.
On May 24, 1980, he was signed by the Hamilton Tiger-Cats after being a year out of football. He was released on June 5.
Staubach incident
Less than two years after his Thanksgiving Day heroics, Longley, under pressure from Danny White for the back-up QB role, left the Cowboys after he punched Staubach during training camp in Thousand Oaks, California. The infamous "sucker punch" occurred after a negative remark Longley made about Staubach to Cowboy teammates. Staubach was putting on his shoulder padson the last day of training camp when Longley hit him in the face without warning and from behind, requiring several stitches to close the wound on Staubach's face. Longley was immediately traded to the San Diego Chargers where he finished his NFL career undefeated as a starter. It was reported that Longley's motivation was he wanted to be traded.
Personal life
Longley earned his nickname the "Mad Bomber" in his rookie training camp because of incidents like one of his errant passes hitting head coach Tom Landry's coaching tower. When the NFL Network did a "Top 10 One-Hit Wonders" list that included Longley, Steve Sabol said he last heard that Longley had ended up selling carpet remnants out of the back of a van in Marfa, Texas.
