The Power defeated the Storm 131-122 in overtime on Thursday night in front of an announced 2,008 fans, who braved the rough winter weather in Summerside.
The teams were tied at 113 after four quarters, but Oshawa overpowered the host team in the five-minute extra frame.
Among the keys to the Power's success was their hot shooting from three-point range, most notably from Morgan Lewis, who shot 5-for-7 from beyond the arc en route to a game-high 38 points and 10 assists.
"The way Oshawa shot the basketball tonight (Thursday), I was surprised we were up as much as we were in that game," said Storm head coach Joe Salerno.
"A team that shoots 46 per cent from three - I mean, they shot from three better than we did field-goal percentage-wise. I told the guys this is one of those games I don't think we lost, but they (Oshawa) won.
"I didn't think we played bad tonight and, to be honest, I don't think we were as bad defensively as the 130 points that were put up."
This was the third meeting between the two teams this season, but the first time Oshawa has visited the Storm.
The loss dropped Summerside to 8-13 (won-lost), keeping them fifth in the National Basketball League of Canada. Oshawa now sits right behind them in sixth at 8-16.
The Power shot 48 per cent from the field Thursday night while the Storm shot 38 per cent, despite being neck-and-neck with Oshawa for most of the game.
Summerside led 51-48 at the half.
The Storm extended their lead to double digits in the fourth quarter, but Oshawa clawed its way back to within striking distance in the final minutes.
"The way Oshawa shot the basketball tonight (Thursday), I was surprised we were up as much as we were in that game. A team that shoots 46 per cent from three - I mean, they shot from three better than we did field-goal percentage-wise. I told the guys this is one of those games I don't think we lost, but they (Oshawa) won. I didn't think we played bad tonight and, to be honest, I don't think we were as bad defensively as the 130 points that were put up." - Storm head coach Joe Salerno
Summerside's Mike Williams went to the free-throw line with his team up 112-111, but made just one of two shots.
Seconds later, Oshawa's Marcus Johnson scored the biggest of his 23 points on a quick drive past the Storm's defence for an easy dunk to tie the game and send it to OT.
The Power would go on to dominate the extra five minutes, with Lewis capping off his big night with back-to-back three pointers.
"Morgan Lewis was virtually unstoppable tonight," said Salerno. "It didn't matter if we switched on him, it didn't matter who we had on him, he had a hell of a game."
Williams added some late free throws to his 15-point, 12-rebound night to make it 126-120. But with time winding down, Summerside was forced to foul immediately, and Oshawa's players closed things out from the line.
Brandon Robinson added 25 points, and Omari Johnson sank 19 for the Power.
Summerside point guard Al Stewart made a surprise return from injury, and contributed the team's first-ever triple-double with a game-high 28 points, 14 rebounds and 12 assists.
The Storm visit the Quebec Kebs on Sunday, before returning to EastLink Arena to host Oshawa again on Friday, Jan. 20.