Born in Malvern in 1893, Leslie Joseph Whitaker Reed was the third child (and eldest son) of Samuel James Reed and the former Mary Ann Kirkus.  He was not only born and bred in Malvern, but lived in that area for most of his life, and was most professionally active there.  Little is known of his education or training; by his own admission, he commenced architectural practice in early 1914.  In May of that year, one of Reed's earliest recorded projects, a "picturesque weekend cottage" in the Dandenongs that he designed and built for his own use, was published in a housing magazine.  He appears to have undertaken little work over the next few years, and it was not until 1922 that his name is recorded as the designer of the Morton-Ray Masonic Temple, an extraordinary Classical pile on Dandenong Road in Malvern East.  That same year, Reed married Una Linda Carson (1896-1977); the couple subsequently moved into a house that he designed and built at the corner of Burke Road and High Street in Malvern East.  They had three children: two daughters (one of whom died as a child in 1938) and a son.

When Reed became registered as an architect in June 1923, he listed his professional address at 967 High Street, Armadale.  At that time, he claimed nine years of architectural experience in Victoria, citing recent projects including a block of residential shops in Elwood and some alterations to a showroom in Flinders Lane.  His subsequent career was largely characterised by residential projects; like many architects of his generation, he embraced a range of fashionable historicist styles in rapid succession, including California Bungalow, Spanish Mission and Tudor Revival.  By the 1930s, when he had relocated his office to 430 Lower Malvern Road in Glen Iris, Reed's practice had expanded to include apartment blocks and small industrial projects, which invariably followed the prevailing Moderne tastes of the day.  During the period, he also designed several houses (notably residences for Arthur Rose at Caulfield and William Stott at St Kilda) that used glazed bricks laid in random courses to create a highly decorative patchwork effect. 

After the Second World War, Reed (by then aged in his early 50s) resumed his practice.  Initially, he continued to design in a historicist mode, typified by a small Colonial-style house in Caulfield (1949) and a late Moderne shopfront at South Yarra (1954).  He had at least partly embraced the modernist style by the late 1950s, when he moved from Malvern to Ringwood.  Reed continued to practise into the early 1960s, mostly designing single residences in the developing post-war suburbs.  He died on 28 May 1964 at the age of 71 years.  He was survived by his wife, his daughter Eira (1927-2009) and his son, J Stuart Reed (1924-), who had followed in the family profession and become a well-known architect (in Brisbane).