Beals made his debut for the Olympics playing under the name W. Thomas on July 27, 1871. The Olympics franchise did not last beyond nine games into their 1872 schedule, and Beals was able to join the Blue Stockings the next season as a second baseman/catcher. He had the best season of his career, hitting .272 with a career-high 24 RBI on 46 hits.
In 1874, Beals started playing under his given name with the perennially powerful Red Stockings. As a part-time second baseman/outfielder, he only managed to hit .196. He reprised his part-time role in the Boston outfield the next season but significantly increased his production, hitting .265. After that 1875 season, the National Association became the National League, and Beals was without a job in Major League Baseball for the next four seasons.