Drafted out of Penn State in 1961, Stewart "Stew" Barber originally signed with Buffalo as a linebacker. It didn't take long for head coach Lou Saban to realize Barber's potential on offense, shifting him to the trenches, where he became the primary architect of the team's pass protection and edge blocking for nearly a decade.

Barber possessed a rare blend of linebacker agility and trench-warfare strength. Settling in at left tackle, he excelled at setting wide, immovable bases against the league's fastest pass rushers, keeping the pocket clean for Jack Kemp. In the run game, his athletic mobility allowed him to seal off defensive ends on the perimeter, creating massive cutback lanes for heavy-hitting backs like Cookie Gilchrist.

Barber locked down the left tackle spot in 1962, earning his first career AFL All-Star selection during a season that saw Buffalo introduce its high-powered offensive attack.

His prime coincided directly with Buffalo's back-to-back AFL Championship runs in 1964 and 1965. Barber was named a First-Team All-AFL selection in 1964 after leading an offensive line that paved the way for Cookie Gilchrist and captured the franchise's first league title. He backed that up in 1965 with his second First-Team All-AFL nod, keeping Jack Kemp protected through a 23–0 championship shutout of San Diego.

Barber remained a model of elite performance, racking up five total AFL All-Star selections (1962, 1964–1967) and adding a Second-Team All-AFL honor in 1966.

Spending his entire nine-year professional career (1961–1969) exclusively with the Bills, Barber played in 122 regular-season games, anchoring the line through the greatest decade in the organization's early history before retiring on the eve of the AFL-NFL merger. In 1998, the organization recognized his contributions to their early dynasty by inducting Barber into the Buffalo Bills Wall of Fame.