After hitting .194 in 23 games, he was sold by the Orioles to the Kansas City Athletics on July 1, 1963, hitting .294 in Kansas City and having a batting average of .272 in 92 games. On June 15, 1964, he was traded back to the Orioles for Wes Stock. On May 31, 1967, he was purchased by the Braves, now located in Atlanta, and on November 27, 1967, he was released by the Braves.
After his playing career ended, Lau became a hitting coach for the Orioles, Oakland Athletics, Kansas City Royals, New York Yankees and Chicago White Sox. Contrary to popular belief, Lau did not emphasize releasing the top hand after making contact with the pitch and following through with only the lower hand on the bat. He did, however, suggest this measure to hitters who—for whatever reason—could not fully extend their arms during their swings.
Lau developed a list of "Absolutes" about hitting, which included:
A balanced, workable stance
Rhythm and movement in the stance (as opposed to standing still)
A good weight shift from a firm rigid backside to a firm rigid frontside
Striding with the front toe closed
Having the bat in the launching position as soon as the front foot touches down
Making the stride a positive, aggressive motion toward the pitcher
A tension-free swing
Hitting through the ball
Hitting the ball where it is pitched, rather than trying to direct it
While serving as the White Sox hitting coach, he died in Key Colony Beach, Florida at the age of 50 after a long bout with cancer. Since his death, no White Sox player or coach (except Lau disciple Walt Hriniak, the Chisox' hitting coach from 1989 to 1995) has worn his number 6 jersey, although it has not been officially retired. The baseball field at Romulus Senior High School in his hometown is named the Charley Lau Baseball Field.