The Devonians took the lead through a Billy Tucker penalty after an Oldland defender had fouled but the home side, still looking for their first points this season, levelled matters before half time through Ali Bamford.
In the second half, Barum increased their lead through Jack Jenkins and then sealed the win with a third through Lee Francis, a victory that takes them to the Division One summit.
Oldland: Perry, Hawkins, Bamford, Day, Planter, Lipinski, Leigh, Hutton, Pearce, Carter, McDowell, Subs: Ingram, Hardiman, Meyendesa