This is the most comprehensive list of Geoffrey's theatre credits that I could find at this point (Thanks Melissa & The now defunct Unofficial Geoffrey Rush Site!).  
NOTE: I realize this list desperately needs to be updated, but I'm having a difficult time finding the information.  If anyone has any input, it would be greatly appreciated.

Year
Theatre Company
Production
Role
1971
Queensland Theatre Company
Wrong Side Of The Moon
Marshall the Raven
1972
Queensland Theatre Company
Lock Up Your Daughters
Brazencourt
1972
Queensland Theatre Company
Assault With A Deadly Weapon
Hinchcliffe
1972
Queensland Theatre Company
Twelfth Night
Fabian
1972
Queensland Theatre Company
Ruling Class
Kelso Truscott
1972
Queensland Theatre Company
You're A Good Man Charlie Brown
Snoopy
1972
Queensland Theatre Company
Puss In Boots
Simple Simon
1973
Queensland Theatre Company
Juno And The Paycock
Joxer
1973
Queensland Theatre Company
Expresso Bongo
Beast
1973
Queensland Theatre Company
National Health
Rees, The Chaplain
1973
Queensland Theatre Company
The Imaginary Invalid
Thomas Diaforus
1973
Queensland Theatre Company
Suddenly At Home
Det. Inspector Appleton
1973
Queensland Theatre Company
Aladdin
Abanzer
1973
Gallery Theatre
Hamlet On Ice
Buttons
1974
Queensland Theatre Company
Godspell
Gilmer
1974
Queensland Theatre Company
The Rivals
Sir Lucius O'Trigger
1974
Queensland Theatre Company
The Philanthropist
Philip
1974
Queensland Theatre Company
Present Laughter
Roland Maule
1975-77
During this time Geoffrey took some time off to go to the following schools: Jacques Lecoq School of Mime, Movement and Theatre, Paris 1975 British Theatre Association Directors' Course, London
1977
Eden Court Theatre, Inverness, Scotland
Jack And The Beanstalk
Chorus Principal
1978
Queensland Theatre Company
King Lear
The Fool
1978
Queensland Theatre Company
Point Of Departure
Monsieur Henri
1978
Queensland Theatre Company
Clowneroonies
Roy the Wonderboy
**Note Geoffrey also directed
1979
Jane Street Theatre
On Our Selection
Dave
1979
Jane Street Theatre
Waiting For Godot
Vladimir
1979
Nimrod Theatre
On Our Selection
Dave
1980
Nimrod Theatre
Teeth And Smiles
????
1981
State Theatre Company of SA
Revengers's Tragedy
????
1981
State Theatre Company of SA
No End Of Blame
????
1981
Sydney Theatre Company
You Can't Take It With You
????
1982
State Theatre Company of SA
A Midsummer Night's Dream
Oberon/Theseus
1982
State Theatre Company of SA
Mother Courage
Soldiers
1982
State Theatre Company of SA
Silver Lining
Toozenbach
1982
State Theatre Company of SA
The Prince Of Homburg
Field Marshall Dorfling
1982
State Theatre Company of SA
Royal Show
????
1983
State Theatre Company of SA
Twelfth Night
Sir Andrew Aguecheek
1983
State Theatre Company of SA
Blood Wedding
The Moon
1983
State Theatre Company of SA
A Midsummer Night's Dream
Oberon/Theseus
1983
State Theatre Company of SA
Netherwood
Dr Eberhard
1983
State Theatre Company of SA
The Marriage Of Figaro
Figaro
1983
State Theatre Company of SA
Pal Joey
Victor
1983
State Theatre Company of SA
The Blind Giant Is Dancing
Allen Fitzgerald
1983
State Theatre Company of SA
Sunrise
David
1984
State Theatre Company of SA for Festival of Sydney
Twelfth Night
Sir Andrew Aguecheek
1984
Theatre Company of SA for the Festival of Sydney
Netherwood
Dr Eberhard
1986
State Theatre Company of SA
Benefactors
David
1987
Belvoir Street Theatre
On Parlaiment Hill
Mouldy
1987
State Theatre Company of SA
Shepherd On The Rocks
Archbishop Wilfred Biggs
1987
State Theatre Company of SA
The Winters's Tale
Autolycus
1988
Melbourne Theatre Company
Tristram Shandy-Gent
Tristram
1988
State Theatre Company of SA
King Lear
The Fool
1988
Belvoir Street Theatre
Les Enfants Du Paradis
Baptiste
1988
Melbourne Theatre Company
The Importance Of Being Earnest
Jack Worthing
1989
The Grin & Tonic Theatre Troupe
Troilus & Cressida
Thersites/Paris
1989
Company B Limited Belvoir Street Theatre
The Diary Of A Madman
Poprishin
1990
State Theatre Company of SA
Marat/Sade
Marat
1990
State Theatre Company of SA
The Comedy Of Errors
Antipholus of Ephesus
1990
Melbourne Theatre Company
The Diary Of A Madman
Poprishin
1990-91
Melbourne Theatre Company National Tour
The Importance Of Being Earnest
Jack Worthing
1991
Sydney Theatre Company
The Government Inspector
Ivan Aleksandrovich Khilestakov
1992
Belvoir Street Theatre Tour: Moscow, St Petersburg
The Diary Of A Madman
Poprishin
1992
Melbourne Theatre Company
The Importance Of Being Earnest
Jack Worthing
1992
Belvoir Street Theatre
The Diary Of A Madman
Poprishin
1992
Sydney Theatre Company
Uncle Vanya
Astrov
1993
Melbourne Theatre Company
The Dutch Courtesan
Cocledemoy
1993
Sydney Theatre Company New Stages
Oleanna
John
1994
Belvoir Street Theatre
Hamlet
Horatio
1995
Belvoir Street Theatre
Hamlet
Horatio

Belvoir Street Theatre