Elsewhere on Friday night there is the first of this season's intra-union derby games, when Ulster are the visitors to the Sportsground.
Connacht will be looking for back-to-back victories and a chance to avenge last season's result when Ulster were the only Irish province not to fall in Galway.
Saturday sees another derby match when Cardiff Blues host the Scarlets at the new Cardiff City Stadium, where the Blues will be bidding to record their first win of the season.
However, the Scarlets have won four of the last five meetings between the two regions.
Also on Saturday, table-topping Edinburgh welcome European champions Leinster to Murrayfield, the ground where the Irish province lifted the Heineken Cup at the end of last season.
Edinburgh, in pursuit of a record-breaking run of victories, will not want Europe's best to spoil their current success.
Both teams have won two out of three games so far this season, but the Dragons sit in second place thanks to a try bonus point bagged in their victory over Glasgow last weekend.
MAGNERS LEAGUE - ROUND 4 FIXTURES:
Friday, September 25 -
Glasgow Warriors v Ospreys, Firhill Arena, 7.05pm (live BBC Wales)
CONNACHT v ULSTER, The Sportsground, 8pm (live Setanta Sports Ireland)
Saturday, September 26 -
Cardiff Blues v Scarlets, Cardiff City Stadium, 6.30pm (live S4C)
Edinburgh v LEINSTER, Murrayfield, 6.30pm (live Setanta Sports Ireland)
Sunday, September 27 -
MUNSTER v Newport Gwent Dragons, Musgrave Park, 5.05pm (live Setanta Sports Ireland/S4C)