McDonald recorded a career-high 67 passes for 1,036 yards and 9 touchdowns in 1965. He was selected to his last Pro Bowl. In 1967 he was traded to the Atlanta Falcons in exchange for a draft choice.
McDonald was picked up by the Cleveland Browns, for whom he caught 7 receptions for 113 yards and one touchdown in the 1968 season. On March 15, 1969, he announced his retirement from pro football.
He was selected for six Pro Bowls, led the league in touchdown receptions twice (1958, 1960), and led the league in receiving yards once (1960). McDonald was the last non-kicker to play in the NFL without a facemask.
McDonald finished his career with 495 receptions for 8,410 yards and 84 touchdowns, the second highest total of touchdown receptions in NFL history at the time. He also rushed for 22 yards and gained 1,459 yards and a touchdown returning punts and kickoffs on special teams, giving him 9,891 career all-purpose yards. He was inducted into the Pro Football Hall of Fame in 1998.