Robbie Keane levelled before Reading's Stephen Hunt and Kevin Doyle combined to make it 2 - 1 to the Irish.
Koumas came up trumps with a late penalty after Cotterill was judged to have been fouled in the box in the closing minutes.
Match Reports
BBC
Wales 2 - 2 Republic of Ireland
Robbie Keane levelled before Reading's Stephen Hunt and Kevin Doyle combined to make it 2 - 1 to the Irish.
Koumas came up trumps with a late penalty after Cotterill was judged to have been fouled in the box in the closing minutes.
Match Reports
BBC