St Johnstone booked their place in next Monday's League Cup quarter-final draw with a 3-1 win over Rangers at Ibrox on Tuesday night.
Murray Davidson and Simon Lappin had Saints 2-0 up at the break and Michael O'Halloran struck just after half-time. James Tavernier pulled one back but it was Tommy Wright's side who progressed as Mark Warburton suffered his first defeat as Rangers boss.
Ross County thumped Falkirk 7-0 at the Global Energy Stadium, helped by a first-half hat-trick from Liam Boyce. Raffaele De Vita, Jonathan Franks, Brian Graham and Darren Holden all scored after the interval for Jim McIntyre's team.
Morton caused an upset by knocking out Motherwell 3-2 after extra time in a dramatic match at Cappielow. Scott McDonald grabbed a last-gasp leveller to cancel out Alex Samuel's early goal but Samuel struck again in extra time to put Jim Duffy's men back in front. Michael Tidser added the third goal before Louis Moult reduced the deficit.
Dundee United came from behind to beat Dunfermline 3-1 after extra time at Tannadice. Michael Paton gave the Pars the lead but Callum Morris equalised before half-time and Scott Fraser and Blair Spittal sent Jackie McNamara's team through with extra-time goals.
Inverness Caley Thistle earned a comfortable 2-0 win away to Livingston thanks to first-half goals from Miles Storey and Danny Devine.
