A stroller (100) has a frame structure with two laterally spaced apart sides and a frame extension (128) on each side. Each frame extension (128) projects rearward and terminates at a free end. The frame structure is collapsible laterally from a side-to-side in-use spacing between the frame extensions (128) to a side-to-side compact spacing less than the in-use spacing between the frame extensions. A push handle is on the free end of each frame extension. A cross-brace (160) extends between and interconnects the frame extensions (128). The cross-brace (160) has a central section and a pair of flanking sections pivotally connected to one another. The cross brace (160) is selectively reconfigurable from a stiff condition to a loose condition with the frame extensions (128) in the in-use spacing. The stiff condition maintains the in-use spacing between the frame extensions (128) and the loose condition permits the frame extensions (128) to collapse to the compact spacing.