He began his career at Blackburn Rovers in 1983, winning the Full Members' Cup with the club in 1987, before moving on to Queens Park Rangers the following year for £400,000.
Barker began his career at Blackburn Rovers under Bobby Saxton's stewardship in 1983, having been Noel Brotherston's boot boy as an apprentice.
Blackburn then dropped down to 19th in 1985–86, just one place and three points above relegated Carlisle United; Barker was voted the club's Player of the Year at the end of the campaign.
Barker played for Rovers in the 1987 Full Members Cup final at Wembley, where Colin Hendry's goal was enough to beat Charlton Athletic 1–0.
Barker helped Rangers post a fifth-place finish in the first-ever season of Premier League football in 1992–93, a feat which made them the top club in London.
However, the sale of top-scorer Les Ferdinand to Newcastle United hit QPR hard, and they were relegated in 1995–96, though Barker did find the net against West London rivals Chelsea.