We present the design and evaluation of the Collaborative Puzzle Game (CPG), a tabletop interactive activity developed for fostering collaboration in children with Autism Spectrum Disorder (ASD). The CPG was inspired by cardboard jigsaw puzzles and runs on the MERL DiamondTouch table . Digital pieces can be manipulated by direct finger touch. The CPG features a set of interaction rules called Enforced Collaboration (EC); in order to be moved, puzzle pieces must be touched and dragged simultaneously by two players. Two studies were conducted to test whether EC has the potential to serve as an interaction paradigm that would help foster collaborative skills. In Study 1, 70 boys with typical development were tested and in Study 2 16 boys with ASD were tested. Results show that EC has a positive effect on collaboration although it appears to be associated with a more complex interaction. For children with ASD, EC was also related to a higher number of "negotiation" moves, which may reflect their higher need of coordination during the collaborative activity.