Manchester United 19 times
The team that won the Scottish Premier League in 1990 was Rangers.
The team that won the Scottish Premier League in 2007 was Celtic.
Preston North End won the first 2 premier leagues (called First Division then). And if your talking first premier league as in the premiership then that was Man United in the early 90's.
Manchester United
They have won 18 league titles
The team that won the Scottish Premier League in 2014 was Celtic.
The team that won the Scottish Premier League in 2012 was Celtic.
The team that won the Scottish Premier League in 2010 was Rangers.
The team that won the Scottish Premier League in 2013 was Celtic.
The team that won the Scottish Premier League in 2005 was Rangers.
The team that won the Scottish Premier League in 2004 was Celtic.