Thinking he needed a change of scenery, McNally requested a trade after the 1974 season; the Orioles obliged, sending him to the Montreal Expos, with whom he played one final year before retiring halfway through 1975, citing an inability to throw the fastball.

After the 1975 season, he added his name to a grievance filed against the reserve clause, which resulted in the historic Seitz decision that created free agency in baseball.

The Royals were in the midst of winning 14 straight state championships when McNally played with them, and the team reached the Legion World Series in two of his years with them.

[9] In 29 games (20 starts) his rookie year, McNally had a 7–8 record, a 4.58 ERA, 78 strikeouts, 55 walks, and 133 hits allowed in 125+2⁄3 innings pitched.

[12] One of them, the second game of a September 7 doubleheader against Kansas City, was one of the shortest starts of his career; he faced four batters, all of whom scored in the Orioles' 6–1 defeat.

[21] On July 21, he was one out away from a complete game against the Detroit Tigers, but with the Orioles leading 6–2, Davey Johnson made an error, allowing a third run to score.

In the fourth game, McNally and Don Drysdale matched four-hitters; one of Baltimore's hits was Frank Robinson's fourth-inning home run for a 1–0 Oriole victory.

In the ninth, with the Orioles up 4–2, McNally retired the first two Angel hitters he faced but surrendered the lead when he gave up back-to-back home runs to José Cardenal and Don Mincher.

[29] Following his first cortisone shot, McNally limited the Chicago White Sox to one run and five hits on July 6 in a complete-game, 5–1 victory.

[36] McNally finished the season among the AL leaders with 22 wins (second to McLain's 31), a 1.95 ERA (third behind Luis Tiant's 1.60 and Sam McDowell's 1.81), 202 strikeouts (fifth), five shutouts (tied with George Brunet for seventh), and 273 innings pitched (fourth).

[10] For his successful return from injury, McNally won the Major League Baseball Comeback Player of the Year Award.

[43] On May 5, he had a no-hitter going until one out in the ninth inning, when Cesar Tovar singled; McNally got Rod Carew to hit into a double play to preserve the shutout.

[51] On June 21, McNally pitched into the ninth inning before being replaced by Pete Richert, limited Washington to two runs, and won his 100th career game as the Orioles defeated the Senators 4–2.

[55] Four days later, he allowed 10 hits in a complete game against the Athletics, but only one run, and he picked up his 20th win of the season as Baltimore defeated Oakland by a score of 5–1.

After walking Leo Cárdenas to lead off the bottom of the inning, he allowed back-to-back home runs to Killebrew and Oliva to make it 4–3.

[61] McNally helped his own cause, depositing a pitch from Granger in the left field seats and becoming the only pitcher in major league history to hit a grand slam in a World Series.

[64] On April 23, he and Clyde Wright of the California Angels held each other's teams to two runs until the ninth, when the Orioles scored six times to give McNally an 8–2 victory.

[66] A sore arm kept McNally from pitching for six weeks in July and August, but he was still the first Oriole to win 20 games when he threw a shutout against the Yankees on September 21.

However, McNally would not allow any other runs, limiting Pittsburgh to three hits and retiring 19 straight hitters at one point in a complete game, 5–3 victory for Baltimore.

[76] McNally was selected to his third All-Star team in 1972, though he lost the game for the AL in the 10th inning when Joe Morgan drove in a run with a single.

He brought it to 17–16, moving his winning percentage over .500 with a victory over the Brewers on September 23, but he lost his last game of the year six days later to finish the season at 17–17.

[98] McNally's 13-year tenure with the Orioles ended when he was traded along with Rich Coggins and minor-league right-handed pitcher Bill Kirkpatrick to the Expos for Ken Singleton and Mike Torrez at the Winter Meetings on December 4, 1974.

Along with Woodie Fryman from the Detroit Tigers, he was one of two left-handed pitchers acquired that day by the Expos which was devoid of southpaws for all but three weeks of the 1974 campaign.

[101] In the first game of a doubleheader on June 8 against the San Diego Padres, he gave up five runs (four earned) over six innings in what would be his last major league appearance.

[105] McNally is known for his role in the historic 1975 Seitz decision which led to the downfall of Major League Baseball's (MLB) reserve clause, ushering in the current era of free agency.

According to John Helyar's book The Lords of the Realm, players' union executive director Marvin Miller asked McNally to add his name to the grievance filed in opposition to the reserve clause, and he agreed.

[1] However, McNally enjoyed a great deal of success against Howard's Senators, whom he defeated 13 times in a row before they moved to Texas after the 1971 season.

[98] Just before the family moved, in late June 1975, McNally checked in to Sinai Hospital in Baltimore with a case of chronic hiccups that had irritated him for nine days.

His son Jeff was drafted by the Brewers out of high school in 1980, but he never played professionally, opting instead to earn a degree at Stanford University.

[1] In a 2004 Sports Illustrated poll asking Montanans to name the "greatest athlete who ever lived in or played for a team in your state," McNally finished third with 9% of the vote, behind Dave Dickenson (19%) and Jan Stenerud (18%).