Jeffery's works have been workshopped and received performances by both prominent Australian ensembles and international artists. Most recently, Jeffery was invited to participate in the Australian String Quartet's National Composers' Forum along with five other young composers. The Quartet premiered String Quartet No. 1 at Adelaide's Elder Hall after a series of workshops led by their composer-in-residence, Andrew Ford.
Short and Suite, a five-movement work for solo viola, placed first in the inaugural Australian and New Zealand Viola Society's Composition Competition in April, 2013. The work was premiered in the same month by violist Gregory McGarity at the Auckland Viola Convention, New Zealand.
Jeffery's first major achievement in the field of composition was in 2011 when he was one of six secondary students selected to participate in the Sinfonietta Project. The project, organised by the Sydney Symphony Orchestra's education team, invited students to compose a work modelled on Ligeti's Chamber Concerto. Vagary, a dectet for woodwind and strings, was workshopped and performed by the Sydney Sinfonia under the baton of Richard Gill.