The bicycle handlebar assembly comprises a handlebar rod and at least one oleo-hydraulic group for controlling on-board bicycle equipment; the oleo-hydraulic group is housed inside the handlebar rod. The internal housing in the handlebar rod overcomes any problems of bulk of the oleo-hydraulic group. Moreover, thanks to the relatively large size of the handlebar rod, the dimensional constraints imposed on the designer are much less stringent with respect to controls associated directly to the brake lever; it is thus relatively easy to make controls capable of exerting very large forces.