Switching from a Pro-Cleveland Democrat to a Republican in 1900, he was appointed by President William McKinley as Assistant Attorney General of the U.S. at the U.S. Department of Justice in the same year, where he served until his resignation in 1903.

In 1917, he left that firm to become senior partner in Beck, Crawford & Harris, and retired from active practice in 1927 to run for Congress from Philadelphia.

[5] He was appointed by President Warren G. Harding as Solicitor General of the United States in 1921 and served until his voluntary resignation in 1925, when he again resumed the practice of law.

In response, Beck wrote The Vanishing Rights of States in which he argued that the U.S. Constitution did not permit the U.S. Senate to exclude a member chosen through an election.

The debate that followed the book's publishing, raising Beck's public profile and making him a prominent option to fill the U.S. House seat vacated by the resignation of James M. Hazlett.

He joined the lawsuit against the New Deal-created Tennessee Valley Authority and argued the case in the Supreme Court in December 1935, declaring the organization unconstitutional and socialistic.

In the final weeks before his death, he served as counsel in the case of an oil stock dealer accused of violating the Securities Act of 1933.