McGrew was born in Indianapolis, Indiana, on June 24, 1880. He was a minor league infielder (playing in his native Midwest) and manager before beginning his umpiring career. By 1929, McGrew was umpiring in the American Association and calling exhibition games for the Pittsburgh Pirates. He spent 1930 and 1931 umpiring in the National League. He umpired in the International League in 1932. McGrew returned to the majors in 1933 and was behind the plate when Dizzy Dean set a National League single-game strikeout record. McGrew requested voluntary retirement in December of that year.
