He was an assistant district attorney of Tarrant County, Texas from 1935 to 1939.

[2] On October 5, 1961, Brewster received a recess appointment from President John F. Kennedy to a new seat on the United States District Court for the Northern District of Texas created by 75 Stat.

He was formally nominated to the same seat by President Kennedy on January 15, 1962.

He served as Chief Judge from 1972 to 1973, assuming senior status on November 1, 1973.

Brewster served in that capacity until his death on November 27, 1979, in Fort Worth.