A last-ditch drive by the Bills with 1:51 remaining only got as far as midfield as Nathan Peterman, on in relief of an injured Tyrod Taylor, was intercepted on a 2-and-20 play from the Bills 48-yard line.
Jacksonville have won the AFC South for the first time ever with defence and the running game. First-year Jaguars head coach Doug Marrone has his first playoff win as a coach - much to Buffalo's dismay.
But, he has his first career playoff win. McCoy carried 19 times for 75 yards and caught six passes for 44 yards.
Come the third quarter Jacksonville cashed in on what proved to be their only red zone scoring chance when Blake Bortles found TE Ben Koyack on fourth-and-goal from the one-yard line near the end of the third quarter.
The first half was filled with rough offense, especially for the Jaguars. If Leonard Fournette is gaining yards in chunks, Bortles won't have to do much and that was the recipe for success this year in Jacksonville. He was 6-of-15 passing for 33 yards.
And that is all up to the Buffalo Bills. Taylor will face a Jacksonville team that sacked opposing quarterbacks on 9.3 percent of dropbacks, which was also the second-highest rate in the league.
The Bills threw it on first down, resulting in an offensive pass interference penalty on receiver Kelvin Benjamin, who was covered by Ramsey.
Both AFC divisional playoff games will air on KDKA-TV.