 He was a partner in the firm of Beith, Stevenson, & Co., 
export merchants of Glasgow and Manchester, and a Director of the Glasgow Chamber of Commerce.At the 1885 general election, Beith was elected as the Member of Parliament (MP) for Glasgow Central, but at the 1886 election he lost the seat in a large swing to the Conservative Party candidate.He was returned to the House of Commons at the 1892 general election as the MP for Inverness Burghs, and held that seat until he stood down at the next election, in 1895.