Hearts and Dundee United qualified for the last 16 of the Scottish League Cup with wins, and fellow top-flight side St Mirren need a point to join them.
Liam Boyce and Finlay Pollock goals against Stirling Albion confirms Hearts' position as Group A winners.
Peter Pawlett, meanwhile, netted before half-time to edge United past East Fife and ensure a fourth win in four.
A goal from Stenhousemuir's Thomas Orr gave St Mirren a fright, but they scored three of their own to win.
League 1 Cove Rangers surprised Championship side Inverness Caledonian Thistle, with two goals in three minutes from Leighton McIntosh and Mitchell Megginson added to by Blair Yule's effort.
It leaves just two points between second and fifth in Group A, although only Stirling and Inverness can harbour hopes of a best runner-up finish.
Ayr United won the evening's early kick-off courtesy of a Cameron Salkeld strike against Hamilton. Four of the five teams in Group E could still finish top heading into the final round of games.
Kilmarnock claimed a potentially priceless bonus point, beating Championship rivals Morton 4-2 on penalties after Kyle Connell's goal cancelled out 17-year-old Lewis McGregor's opener for the Greenock side.
Clyde won 4-2 on penalties in the other Group G game after Lowland League East Kilbride held them at K-Park. It means Clyde, Kilmarnock and Stranraer go into the final game with hopes of winning the group.
Kelty Hearts also gave themselves a fighting chance of a best runner-up spot in Dundee United's group after coming from behind to beat Elgin City.
Queen's Park's 2-1 victory over Annan Athletic means Motherwell can win Group F on Wednesday when they face Airdrieonians. Laurie Ellis' team currently top the group by two points, but have played all their matches.
Partick Thistle beat Dumbarton 2-0 in Group H but need a substantial victory over St Mirren if they are to progress.
Scottish League Cup results
Cove Rangers 3-1 Inverness Caledonian Thistle
Stirling Albion 0-2 Hearts
East Fife 0-1 Dundee United
East Fife 1-3 Kelty Hearts
Brechin City 1-0 Alloa Athletic
Hamilton Academical 0-1 Ayr United
Annan Athletic 1-2 Queen's Park
East Kilbride 2-2 Clyde (2-4 pens)
Kilmarnock 1-1 Greenock Morton (4-3 pens)
Stenhousemuir 1-3 St Mirren
Partick Thistle 2-0 Dumbarton