Kapur fought back from three bogeys in first six holes for an even par 72, while compatriot Himmat Rai (69) finished Tied-36th.
Kapur once again started with three bogeys only to make up later but was unable to force the pace needed to get into Top-10, Himmat also had a nice little birdie run from 10th to 13th, but also gave away a couple of bogeys. Gaganjeet Bhullar (72) was Tied 52nd and Chiragh Kumar (75) was Tied-71st.
Despite the spirited challenges from France's Alexander Levy and Australia's Jason Scrivener, Oosthuizen kept his composure to win the AUD 1.75 million event by one shot at the Lake Karrinyup Country Club.
Kapur said, "Rollercoaster is the best word to describe the week. I had a good start where I started with a six-under and I ended the week with a six-under total. I proud of how I fought back considering the start I had today. There have been lots of positives in the game. I think the long game is pretty good but feeling a little disappointed over the weekend as I didn't hole any putts. I started off with a three-putt in the first and second holes today.
Himmat said, "I absolutely love playing in Australia and it's nice to be back here. I've never played on a track like this before. It was hard and fast and demanded a lot of different kind of shots. I hit the ball very well in patches and if my putting was better, I would have finished higher up. Overall I'm very pleased with how my week has ended in Perth."