A quick-release adjustable mounting bracket to be detachably connected to, for example, a handlebar of a bicycle to permit, for example, a bright flashing light source to be attached to and removed from the handlebar without the use of tools so that neither the mounting bracket nor the light source need remain attached when the bicycle is not in use. The mounting bracket includes a grip to engage a portion of the handlebar and a light stand pivotally coupled to the grip. The light source is removably received by the light stand so that the light stand and the light source received thereby are rotatable relative to the grip. The grip includes a hook-shaped locking catch, a coupling cavity within which a plurality of spaced, parallel-aligned coupling pin retaining slots are formed, and a flexible clamping band. A locking latch pivotally coupled to a first end of the flexible clamping band is pulled towards and rotated into locking engagement with the locking catch. The flexible clamping band is adapted to be bent over the locking bar, whereby a coupling pin carried by the opposite end of the clamping band is releasably connected to one of the plurality of coupling pin retaining slots in the grip depending upon the size (e.g., diameter) of the handlebar to which the mounting bracket is to be detachably connected.