Margaret McDowall had the following podium finishes at major championships: 1st in the 1954 British Empire and Commonwealth Games 3×110 yards Medley Relay (with Elenor Gordon and Margaret Girvan). In the 1954 British Empire and Commonwealth Games 110 yards backstroke McDowall finished fifth. In the British Empire and Commonwealth Games she competed for Scotland.
|1952 Summer||16||Helsinki||Swimming||Women's 100 metres Backstroke||Great Britain||GBR||7|
|1952 Summer||16||Helsinki||Swimming||Great Britain||Final||7||1:18.4|
|1952 Summer||16||Helsinki||Swimming||Great Britain||Round One||Heat One||3||QU||1:17.5|