“Margaret Penrose” is a Stratemeyer Syndicate pseudonym used for a few series published by Cupples & Leon.
The first series to use this name was the Dorothy Dale series (1908—1924), which became the Syndicate’s first long series with a girl protagonist.
Based on this success, the name was also used on the Motor Girls series (1910—1917), a counterpart to the successful Motor Boys series (1906—1924).
The Radio Girls series (1922—1923) was the last new series to use this name. When the series was sold off to Goldsmith, it became a Campfire Girls series in 1930.
One book published under the “Margaret Penrose” name that was not a Stratemeyer Syndicate property was The Burglar’s Daughter (Jordan, Marsh, 1899). The Syndicate pen name being the same was a coincidence.