1983–2010: The Borough of Ogwr wards of Bettws, Blackmill, Blaengarw, Caerau, Llangeinor, Llangynwyd, Maesteg East, Maesteg West, Nantyffyllon, Nant-y-moel, Ogmore Vale, Pencoed, Pontycymmer, St Bride's Minor, and Ynysawdre, and the Borough of Taff-Ely wards of Brynna, Gilfach Goch, Llanharan, and Llanharry.

2010–2024: The Bridgend County Borough electoral divisions of Aberkenfig, Bettws, Blackmill, Blaengarw, Bryncethin, Bryncoch, Caerau, Cefn Cribwr, Felindre, Hendre, Llangeinor, Llangynwyd, Maesteg East, Maesteg West, Nant-y-moel, Ogmore Vale, Penprysg, Pontycymmer, Sarn, and Ynysawdre, and those in Rhondda Cynon Taff County Borough of Brynna, Gilfach Goch, Llanharan, and Llanharry.

[2] A substantial change of boundaries took effect in 1983, when the new constituency of Bridgend was created, centred on the town of that name, which was by then the largest settlement in Ogmore.

[3] Successive candidates fielded by the Labour Party have won absolute majorities (pluralities) since the seat was created in 1918, or have run unopposed four times.

The highest polling of any runner-up, by percentage, was Thomas George Jones in 1931, winning 30.8% of the votes cast, 0.3% more than half the percentage polled by the winning candidate; this was when the Labour Party's vote was slightly split by the presence of a prominent Communist Party candidate and editor, Johnny Campbell.