Adam Matthews netted a second-half brace as Celtic easily handled Kilmarnock, 4-1, on Wednesday at Celtic Park.
Joseph Ledley opened the scoring for the hosts four minutes from the interval, but the visitors equalized in the 48th minute through Cillian Sheridan.
Two minutes later, Matthews bagged his first of the contest to give the hosts the lead for good. Anthony Stokes made it 3-1 for Celtic 12 minutes from time and Matthews sealed the result with his second of the match in the 83rd minute.
The result sees Celtic increase its lead atop the league to a comfortable 15 points over second-place Inverness, which suffered a 2-1 setback to St. Mirren at St. Mirren Park thanks to an 82-minute go-ahead tally from Steven Thompson.
St. Johnstone earned a comfortable 3-1 win over Aberdeen on Wednesday at McDiarmid Park. The hosts opened the scoring in the 33rd minute via a strike from Gregory Tade, but 11 minutes later, Aberdeen found an equalizer through Niall McGinn.
After the interval, the home side secured the result with tallies from Rowan Vine and David Mackay just two minutes apart.
Elsewhere on Wednesday, John Sutton's goal four minutes from time lifted Hearts to a 1-0 win over 10-man Dundee at Tynecastle Stadium, while Ivan Sproule gave Ross County a 1-0 victory over Hibernian with a 36th-minute tally at Victoria Park.