This was one of five gold medal performances in Olympic boat classes by the GB squad, along with four silvers and two bronzes, a performance that puts Britain in overall top spot ahead of Germany. Britain also took four medals in Paralympic classes, including two golds.
Five-times world champion Grainger had been forced to race with Wilson this weekend following the decision to let her regular partner and fellow-reigning world champion Anna Watkins fully recover from a back tweak.
However, this seemed to make no difference as, after a brief show by Austria in the opening half-dozen strokes, the British duo moved into a lead they were never to give up and they comfortably moved ahead of the field as the race unfolded. At the line, Grainger and Wilson had more than a length of clear water ahead of USA and Belarus.
Despite this win, Wilson is liable to be replaced by Watkins in the next World Cup event in three weeks' time. Grainger was clearly pleased with the win in her makeshift crew - "that was a good race" was her straightforward summary. She added: "It was enjoyable because we felt no pressure. But we knew we could be fast. We have simply been working on the important things, not the tiny little adjustments you make when you have been together longer."
However, it is clear she sees this competition as just another stepping stone towards next year's London Games and the one big omission from her medal collection - Olympic gold. "I started out in the single two seasons ago and now we're at the start of my second season in the double - it's all come around surprisingly quickly," she said.
Earlier, Lossiemouth's Heather Stanning and her world silver medal partner Helen Glover were equally as dominant in winning women's pairs, ahead of USA and the Netherlands. This was the first-ever international victory for this pair and not surprisingly, Stanning confirmed "we're really happy to win here" while Glover said: "We were really ready to race".
Edinburgh's Lindsey Maguire has been promoted into the stroke seat of the women's eight for this season and she drove her crew-mates to a strong silver medal behind the Netherlands and ahead of Romania.
Britain's other medals in Olympic classes were gold in men's pairs and fours, and women's lightweight doubles; silver in men's doubles and eights and - by the squad's second crew - women's lightweight doubles; bronze in lightweight men's fours and women's quadruple sculls, both crews being reigning world champions.
Dunfermline's Dave Smith was in the British adaptive four that won their Paralympic event.