Ressler was a star center on the Mahanoy Joint team, playing both offense and defense in the era of the single platoon system.

[4] Joining Ressler on the select list was future Pro Football Hall of Fame quarterback Joe Namath from Beaver Falls.

[1] As freshmen were prohibited by NCAA rule from participation in varsity sports, Ressler spent the 1962 season playing for Penn State's freshman football team, where he distinguished himself as a center on offense and a linebacker on defense.

[6] The Penn State athletic department began touting Ressler as a potential All-American for 1964, with publicity director Jim Tarman noting: "If we have an All-America candidate next year, he's it.

Ressler finished the 10 games of his junior 1963 season with 7 quarterback sacks, 3 fumble recoveries, an interception, 53 unassisted tackles, and 30 assists.

[6] Penn State head coach Rip Engle moved Ressler from guard to center on the offensive side for his 1964 senior season.

[9] The enthusiastic coach told another reporter of his senior two-way line star, "Ressler is big, strong, quick, a fine tackler, and what else do you need?

[13][14] Ressler — called "Zeke" by his Penn State teammates[15] — was chosen as winner of the Maxwell Award as college football's best all-around player of 1964.

[22] In a draft that saw Illinois linebacker Dick Butkus taken as the top run-stopper and Northwestern's Joe Cerne taken as the first center off the board, Glenn Ressler was selected by the Baltimore Colts in the third round with the 36th overall pick.

[2] He was estimated more highly by the rival American Football League (AFL), with the Denver Broncos taking him with the 18th overall pick in that draft.

"[19] Ressler spent his rookie year under head coach Don Shula in a reserve role, substituting at both offensive and defensive tackle.

[27] The Colts' had Ressler report early with the rookies to its 1966 training camp so that head coach Don Shula could give the second year player multiple repetitions at a new NFL position, center.

Ressler continued to play several positions in a reserve roll for the Colts in 1966, finally getting his first professional start in a November 20 game against the Detroit Lions at Tiger Stadium in the season's 11th week.

[33] On January 12, 1969, Ressler started at left guard for the Colts in Super Bowl III, a 16–7 loss to Joe Namath and the New York Jets.

[36] From 1971 through the end of his career in 1974, Ressler was a reliable starter at left guard for the Colts, albeit missing 5 games in 1972 due to injury.

[2] While still playing for the Colts, Ressler was in the restaurant business with his father-in-law, operating Red Barn and Ponderosa Steakhouse franchises, which continued after his career ended.