His daughter, Angela Marriott, told The Associated Press that Briscoe, 76, died of pneumonia at a hospital in Norwalk, California. He had been hospitalized with circulation issues in his legs.
Briscoe was inducted into the College Football Hall of Fame in 2016 following three consecutive conference titles for Omaha University where he sent 22 school records, including completion percentage, passing yards and total touchdowns.
Denver didn't give him a chance to compete for the quarterback job in 1969, so he asked to be released. He became a Pro Bowl receiver with the Buffalo Bills.
James Harris was Briscoe's roommate with the Bills in 1969, and Briscoe helped Harris become the first Black quarterback in the AFL to open a season as a starter.
In 1974, Harris played for the Los Angeles Rams and became the first Black quarterback to win an NFL playoff game. He also was Pro Bowl MVP that season.
Well after his playing days were over, Briscoe remained very vocal about racial injustice. He was proud to have moved the needle in 1968, but he told The Associated Press in 2018 that he was disappointed that the multiple strides he made in his days had been lost.