Comprising of St John Vianney , St Peter in Chains, and St Mary and St John the Baptist, known as Pleasington Priory, the parish of St Oscar Romero serves the south west area of Blackburn and the parish boundary is described below.
The boundary on the south is the M65 and continues westerly up to the diocesan boundary which follows the river Roddlesworth to its confluence with the river Darwen and then along the river Darwen through Houghton Bottoms to its meeting with the Alum House Brook and along this brook and then Arley Brook up to but excluding Arley farm. The boundary then goes south by the tracks passing by but including Westholme school and across Meins Road to Billinge End Road.
The boundary then turns east along Billinge End Road to and along Killards Lane and the track to Under Billinge Lane and follows this lane then goes into Lawley Road and Billinge Avenue both of which are wholly in the parish of Sacred Heart and St Anne. It reaches Buncer Lane and follows this to its junction with Wensley Road.
The boundary goes along Wensley Road up to Garden Street and then follows Garden Street to the junction with Redlam and the A674 at Griffin. Then it follows King Street, Higher Church Street and Church Street to Railway Road where the boundary goes towards the Railway station and turns south to follow the railway line to the Wainwright Bridge. This means the Anglican Cathedral is in the new parish.
The boundary now goes over the bridge then turns south down Bolton Road to the Aqueduct and Empire Theatre at Ewood. The River Darwen becomes the boundary again until the meeting with Fore Street in Lower Darwen. Leaving the river the parish boundary follows Sandy Lane up to Bolton Road and then follows the M65.