Gregor notched an assist, two shots on goal and two hits in Saturday's 3-2 overtime win over the Bruins.
Gregor scored a goal on four shots and added four PIM in Tuesday's 8-1 win over the Blues.
Gregor signed a one-year, $850,000 contract with the Senators on Monday, Jason Gregor of Sports 1440 Edmonton reports.
Gregor will become an unrestricted free agent Monday after not receiving a qualifying offer from the Maple Leafs, Elliotte Friedman of Sportsnet reports.
Gregor, who put up six goals and six assists in 63 games this season, has been a healthy scratch in the first round of the Eastern Conference playoffs.
Gregor (illness) returned to practice Wednesday and wore a regular jersey, per Terry Koshan of The Toronto Sun, which suggests he should be available Thursday versus the Islanders.
Gregor (illness) won't play Tuesday against the Sharks, according to NHL.com's Dave McCarthy.
Gregor scored his third goal of the season and added the shootout winner in Tuesday's 2-1 victory over the Panthers.
Per Chris Johnston of TSN. Gregor agreed to a one-year contract worth $775,000 with Toronto on Tuesday.
Gregor signed a professional tryout agreement with Toronto on Wednesday.