After spending the 1952 season with the AAA St. Paul Saints, Terwilliger was claimed off waivers by the Washington Senators following the 1952 season and spent the next two seasons as the Senators' second baseman. Prior to the start of the 1955 season, Terwilliger switched teams again after the New York Giants purchased him from the Senators. He spent the 1955 and '56 seasons shuttling between New York and AAA Minneapolis and the entire 1957 season at AAA. Following the 1957 season, he was traded to the Detroit Tigers in a swap for fellow journeymen infielder Jack Dittmer. After spending 1958 with the Tigers' AAA Charleston Senators, he was acquired by the Kansas City A's from the Detroit Tigers in the December 1958 Rule 5 draft. In 1959, Terwilliger saw his last large stretch of time in the majors, playing 74 games at second and shortstop for the A's. After starting the 1960 season with the A's, Terwilliger was unofficially traded to the New York Yankees, a transaction that was common at the time between the two teams when the Yankees were accused of using the A's as a major league farm club and the two teams often seemed to have mutual rights to each other's players, and played the rest of the season at AAA Richmond Virginians before retiring as a full-time player. In 666 games over nine seasons, Terwilliger posted a .240 batting average (501-for-2091) with 271 runs, 22 home runs, 162 RBI and 247 bases on balls. Defensively, he recorded a .974 fielding percentage playing primarily at second base. Coaching career After his playing days were over, Terwilliger started a successful career as coach and minor-league manager in the Yankees' organization with the Greensboro Yankees of the B-level Carolina League. After taking the 1962 season off, Terwilliger would be hired by the Washington Senators to manage their single-A team, the Wisconsin Rapids Senators in the Midwest League. He would spend the following six seasons managing in the Senators organization, the last two at AAA. Under manager Ted Williams, Terwilliger was the third-base coach of the Senators from 1969 to 1971 and of the Texas Rangers in their first season, 1972. Following the season, Terwilliger was let go by the Rangers, following Williams' retirement, and would manage the Houston Astros' AA Columbus Astros in 1973 and Texas' single-A Lynchburg Rangers in 1975 before spending the next four seasons