A fire that burned out more than 350 hectares of grassland southwest of Melbourne has been brought under control.

It took 40 CFA crews and four aircraft, including Elvis the Aircrane, almost four hours to get on top of the Little River blaze.

The fire broke out at 3.30pm (AEDT) and was brought under control at 7.20pm.

The slow moving grassfire travelled northwest under the influence of a south-easterly wind and at times proved dangerous and difficult to battle.

At one stage the fire was spotting 2-3 kilometres ahead while stony ground made access for tankers difficult.

Crews will remain on scene throughout the night patrolling the fire's edge.

Its cause is being investigated.