MacGibbon formed her string quartet in 1936, going on to perform regularly around the UK, and frequently broadcast on the BBC.[1][4] The MacGibbon Quartet gave regular concert series at London's Conway Hall from 1936 to 1969.[5] As well as in her own quartet, MacGibbon performed many times with others over the course of her career, including with well-known ensembles such as the English Chamber Orchestra.[1]
She was a founding member of the London Mozart Players under Harry Blech.[1] Blech praised MacGibbon as an excellent player, saying: “I always liked to have her near the front".[2]
The Musical Times wrote that:
For Margot MacGibbon, versatility was both a professional strength and source of personal pride; but perfectionism of craft was no less central to her approach music.[5]
In 1979, MacGibbon co-founded The Sascha Lasserson Memorial Trust, serving on the panel of adjudicators for the international Lasserson Memorial Violin Competition.[1][6][2]
Margot MacGibbon continued playing into her nineties, even after suffering a stroke.[1] She still taught, and prepared pupils for exams, at the age of 90.[2]
She died in London on 4 September 1998.[1] The Times remembered her as "a musician of formidable character, and natural talent", and "a tiny, colourful and complex person".[2] In 1999, the Margot MacGibbon Award for an Australian violinist was established at the Royal Academy of Music, in her memory.[7]