McGregor was acquired along with Rick Dempsey, Tippy Martinez, Rudy May and Dave Pagan by the Orioles from the Yankees for Ken Holtzman, Doyle Alexander, Elrod Hendricks, Grant Jackson and Jimmy Freeman at the trade deadline on June 15, 1976.

"The kid can pitch, that's all I can say," praised Hall of Fame manager Earl Weaver after McGregor threw a shutout on June 24 of that year.

[citation needed] In the 1983 postseason, McGregor allowed only two runs in the openers of the ALCS and World Series, but lost both games by scores of 2–1 to the White Sox and Phillies, respectively.

In 356 pitching appearances covering 2,140.2 innings, he committed only nine errors in 445 total chances for a .980 fielding percentage, which was 24 points higher than the league average at his position.

[8] After his baseball career ended, McGregor worked as a youth pastor and for five years headed a church in Towson, Maryland.