Lau was signed by the Detroit Tigers as an amateur free agent. After spending three seasons with the organization (1956, 1958–59) he was traded (with Don Lee) to the Milwaukee Braves for Casey Wise, Don Kaiser, and Mike Roarke. After the Baltimore Orioles purchased him from the Braves in , he adopted a contact hitter's batting stance (feet wide apart, bat held almost parallel to the ground). That season he had a .294 batting average with six home runs and 37 runs batted in.