Crues meanwhile stayed five points clear of Linfield at the top of the table
New Glentoran manager Gary Haveron says he's gutted about losing to Linfield on Saturday, but is taking away positives from his first game in charge.
The Oval showdown was heading for a draw, until former Glens defender Jimmy Callacher headed home three minutes from time to give the Blues a hard-earned 2-1 victory.
Haveron is praising his players and says he wants more of the same in the coming weeks.
There was also late drama in the other big Belfast derby with league leaders Crusaders battling back from 3-0 down to beat Cliftonville 4-3 at Seaview.
The Crues stay five points clear of Linfield at the top of the table.
In the rest of the derby games -
Jordan Allan struck twice in the dying minutes as Coleraine drew 2-all with visiting Ballymena.
Glenavon beat 10-man Portadown 1-0 in Lurgan.
And Ballinamallard defeated Dungannon 2-0 at Ferney Park.
Meanwhile, Ards had a 3-1 home win against Carrick.
Results Saturday October 1
Ballinamallard United 2-0 Dungannon Swifts
Coleraine 2-2 Ballymena United
Crusaders 4-3 Cliftonville
Glenavon 1-0 Portadown
Glentoran 1-2 Linfield
Ards 3-1 Carrick Rangers