Ferguson placed in the top 10 in pass attempts five times, completions and passing yards four times, passing touchdowns six times, and yards per pass three times. At one time he shared, with Ron Jaworski, the NFL record for consecutive starts by a quarterback with 107, until he was replaced by Joe Dufek on September 30, 1984. He has a 1–3 record in the NFL postseason, winning against the New York Jets in 1981. His three losses came from the Cincinnati Bengals in those same playoffs, the San Diego Chargers the year before in 1980 (a game in which he played the entire contest with a sprained ankle), and in 1974 to the Pittsburgh Steelers. He retired after the 1990 season after playing only one game with the Colts.
Ferguson's best season came in 1975, when he tied Fran Tarkenton for the NFL lead with 25 touchdown passes and compiled a passer rating of 81.3. Ferguson also surpassed 20 touchdown passes in three other seasons (1980, 1981, 1983).
Ferguson is one of few quarterbacks who started immediately as a rookie, and his team won four of his first six starts. He is one of only two rookie quarterbacks to accomplish this feat, being joined by the Atlanta Falcons' Matt Ryan in 2008.
In 1993, Ferguson was inducted into the Bills' Wall of Fame. Seven years earlier, he had been inducted in the National Federation of State High Schools Association's Hall of Fame in 1986 for his outstanding play at the high school level. The number 12 has been retired by the Bills in honor of both Ferguson and Jim Kelly. He is also in the Arkansas and Louisiana halls of fame. He returned to football in 1995 when, at the age of 45, he signed a contract with the San Antonio Texans of the Canadian Football League. He retired at the end of the year to become the quarterbacks coach at the University of Arkansas. He later coached at Louisiana Tech University, Ruston High School, and Captain Shreve High School in Shreveport as head coach. He has since returned to Arkansas and is in the commercial/residential real estate business.