Margaret River is three hours south of Perth and one of Australia's finest wine regions — Cabernet Sauvignon and Chardonnay are the benchmarks, but Semillon Sauvignon Blanc blends and Shiraz are also excellent. The region is genuinely worth a dedicated trip, but Perth's better restaurants carry extensive Margaret River lists, and several wine bars and bottle shops in the city make it easy to explore the region's output without leaving town. If you are planning even one good dinner in Perth, it is worth asking for a Margaret River recommendation.
The wine is only part of the story. Margaret River also produces excellent olive oil, cheese, craft chocolate, and artisan bread, and many of the wineries have restaurants attached that are among the better places to eat in Western Australia. Day trips from Perth are possible but long; a better plan is to stay two or three nights in the region, which allows you to drive the wine road properly and visit the spectacular coastline at Cape Leeuwin and around Margaret River town. For a taste without the trip, Perth's QV1 bottle shop and the wine bars of Subiaco carry good regional selections and knowledgeable staff.