[3] In 1979, Simon appeared again on The Mike Walsh Show, singing "Australia Be Proud" with the Marist Singers of NSW, with Artistic Director Paul Bateman.
With his own musical theatre company Essgee Entertainment, Gallaher produced and acted in stage productions of The Pirates of Penzance, H.M.S.
In 2015 he took over the role of The Wonderful Wizard of Oz in the Australian production of Wicked and opened with it at the commencement of the Brisbane season.
Gallaher recently directed a new production of his version of The Pirates of Penzance, which played at the QPAC to celebrate the 30th Anniversary of the Arts Centre and of the show's original opening.
He is a member of Live Performance Australia (LPA) and sits on the Helpmann Awards nominating panel for Musical Theatre.