The tournament will continue on Friday as top-ranked Ottawa faces reigning two-time CIS champion Queen's and host Victoria takes on Trinity Western in semifinal play.
Kayla Jones, Krista Draycott and Vanessa MacMillan scored for the top-ranked and OUA champion Gee-Gees on Thursday.
Jessica Furtado scored the lone goal for the Capers, who are out of medal contention.
"I thought we played really well today and credit to Cape Breton, who were very good on the counter attack," said Ottawa coach Steve Johnson. "We got an early goal, which gave us a good chance to settle down throughout the rest of the game."
Jones, a rookie striker, scored in the fourth minute, getting her head on a left-footed cross from Draycott.
Furtado tied the game eight minutes later, pouncing onto a rebound from a shot by Tara Rogers that hit the left post.
Ottawa regained the lead in the 26th minute when Draycott scored directly off a corner kick that curled into the net.
MacMillan, a rookie and second-half substitute, put the game out of reach with an 80th-minute goal, chesting down a cross from Chiara Quadri and firing a low and hard shot.
"We knew going down a goal early to Ottawa was going to make it tough," said Capers coach Ness Timmons. "Ottawa is a good team and I thought we did do a good job opening it up in the first half."
Trinity-Western Spartans 2, Laurier Golden Hawks 2-1
At Victoria, the Canada West champion Spartans advance to the second semifinal a year after TWU lost a heartbreaker against McGill in the first round, 1-0 on kicks, en route to a sixth-place finish.
"Our finishing wasn't as sharp as it could have been but full credit to them as they kept going all the way until the very end," said Spartans head coach Graham Roxburgh of Thursday's win. "Anytime you get to this level it's going to be competitive. It's never going to be easy. They are a very good team."
Queen's Gaels 2, Dalhousie Tigers 0
At Victoria, the reigning two-time national champion Gaels prevailed over Dalhousie to advance to the semifinal round for the fourth consecutive year.
Queen's got goals from Alexic McKinty and Riley Filion.
"It was great to get a win against a very good team," said Dave MacDowel, head coach for the Gaels. "We took some time to adjust to the grass and the bigger surface but we scored a couple nice goals and were unlucky not to get more in the second half."
Victoria Vikes 2, Sherbrooke Vert et Or 1
At Victoria, the tournament host Vikes defeated Sherbrooke to advance to the national Final Four for the first time since 2008, which marked their last appearance at the national tourney.
The Vikes received a goal each from midfielders Jackie Harrison of Whitehorse and Tessa Margetts of Victoria, while Chloe Belhumeur Limoges of Drummondville, Que., was the lone scorer for Sherbrooke.
"I thought we played very well in the first half and we had one or two very good chances that we didn't finish," said Tracy David, Vikes head coach. "Credit to Sherbrooke because they came back and scored one and they just kept coming and coming. They were very dangerous and it was a nail biter of a game."