Celtic showed their mettle to sink St Mirren as Oh climbed off the bench to grab a late winner and secure a vital 2-1 come from behind win.
Conor McMenamin netted the opener to spark a blame game inside the champions' box, David Turnbull levelled eight minutes later and for long spells it seemed it might not be the champions night until a late winner.
But the lethargy which blighted the stalemate against Hibs on Saturday was gone and South Korean striker Oh's goal came amid mounting pressure in the final 10 minutes.
A dangerous cocktail of absent ultras and missing talent hinted towards a challenging night for Celtic. And that inkling became a reality after seven minutes when McMenamin ghosted between Liam Scales and Greg Taylor.
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