Scotland 320 (McMullen 136, Berrington 60, Bilal Khan 5-55) beat Oman 244 for 9 (Khushi 69, Greaves 5-53) by 76 runs
Bulawayo: Ireland's defeat to Sri Lanka at Queen Sports Club ensured that both Oman and Scotland make it to the Super Six.
But Scotland will also have the added advantage of carrying two points from today's win over Oman to the next stage.
Oman got off to a slow start, with Kashyap Prajapati and Jatinder Singh adding merely 25 runs in the first 10 overs.
The pent-up pressure led to Prajapati's fall in the 11th over when centurion McMullen cleaned him up. Soon after, Jatinder (14) also fell to Adrian Neil.
Zeeshan Maqsood and Aqib Ilyas then held the innings together with a 32-run stand, before Maqsood went for a slog sweep and was bowled by Michael Leask.
One brought two as Aqib Ilyas was accounted for by Mark Watt in the very next over.
A resilient stand for the fifth wicket between Mohammad Nadeem and Ayaan Khan added 30 runs. With Nadeem's fall in the 30th over, Oman had lost half their side and needed almost 11 runs an over to win the game.
An enterprising seventh-wicket partnership of 105 between Naseem Khushi (69) and Shoaib Khan (36) brought some entertainment to the proceedings late in the day, but by then Scotland's grasp over the encounter was complete.
Chris Greaves (5/53) picked his maiden five-for during this innings.
Earlier in the day, Scotland overcame a jittery start to post a challenging total against Oman.
Bilal Khan gave Oman the perfect start when he trapped Christopher McBride lbw off the very third ball of the game.
Scotland found the going tough against a disciplined new-ball effort from the Gulf side, and could muster merely two runs off their first four overs.
Matthew Cross and Brandon McMullen gradually settled in and picked up the scoring rate.
The duo added 82 runs and McMullen brought up his half-century, comprising of four fours and three sixes, during the stand.
In the 19th over, Jay Odedra finally brought a breakthrough for Oman when he got Cross (27) to play on a delivery.
Skipper Richie Berrington then joined hands with McMullen and steadied the innings.
With time, Berrington grew comfortable at the wicket, while McMullen continued at a swift pace.
The latter brought up his maiden ODI century in the 32nd over. The pair added 100 runs off merely 97 balls.
After McMullen's ton, Scotland batted with extra urgency, adding 58 runs in overs 33-38. Berrington brought up his 17th ODI fifty in this period.
The Scotland captain was finally run out in the 39th over when trying to take a run off a misfield.
A few overs later, McMullen (136) also fell to Bilal while trying to up the scoring rate.
A couple of more strikes by Bilal pegged the Scottish innings back. But crucial contributions from Tomas Mackintosh (32) and Mark Watt (25) late in the game helped the European side cross 300.
Bilal was the pick of Oman bowlers and finished at 5/55.
Earlier, Oman won the toss and elected to bowl against Scotland.
Richie Berrington's men boast a 4-1 winning record in six ODIs across League 2 (one no result).
Zeeshan Maqsood confirmed that the Omanis come in with an unchanged side despite their heavy defeat to Sri Lanka, while Scotland opted to include fast bowler Adrian Neill.