Dallas arrived at Sixfields at the start of October on an initial one-month loan, which was duly extended until January 1.
The 22-year-old made a total of 12 appearances for the Cobblers, 10 of which were starts, and scored three goals.
Brentford manager Mark Warburton told the League One club's official website: " The idea of the loan was to allow the player to continue his development through regular and consistent pitch time and we have been delighted by both the amount he has played and the level of his performances over the last few weeks.
"Stuart returns to the squad match fit and in good shape to play his part for the Christmas programme and the second half of the season."
Dallas's recall means he will not now be available to face Burton, Portsmouth and Chesterfield ahead of what would have been his scheduled return to Griffin Park on New Year's Day.
Assistant manager Andy King will be in charge of Northampton at Burton on Boxing Day following Aidy Boothroyd's sacking in the aftermath of Saturday's 4-1 home defeat to Wycombe.
- Sports & Recreation