A 19-year-old victim inside the house followed the group in his car, trailing them to the vicinity of Glenhuntly Road and Allison Street in Elsternwick.
Moments later, the stolen Mercedes reversed into the victim’s car, causing substantial damage.
Police said the offenders fled the scene.
The stolen BMW was discovered by police on Villiers Street in Elsternwick later in the morning, and the Mercedes remains outstanding.
The male offenders who stole the BMW are described as being in their mid to late teens, with one man wearing a black jacket over a grey hoodie and grey tracksuit pants.
Another was wearing a black hoodie with an orange Nike logo in the chest area and black and grey tracksuit pants.
One of the other men, who allegedly stole the Mercedes, was wearing a dark hoodie, dark-coloured shorts and black slide-on shoes, while the other wore a light-coloured hoodie, dark pants, and dark shoes.
Police believe the stolen Mercedes was seen on Heatherton Road in Noble Park just after midday.