A mechanical timepiece oscillator includes, between a support and an inertial element, a flexure bearing with flexible strips crossed in projection, including, superposed, an upper level that includes, between an upper support and an upper inertial element, an upper primary strip in a first direction and an upper secondary strip in a second direction, and a lower level that includes, between a lower support and a lower inertial element, a lower primary strip in the first direction and a lower secondary strip in the second direction. The upper level and lower level include, between the support and the upper or respectively lower support, a translational table with an elastic connection along one or two axes of freedom in the oscillation plane, of lower stiffness than that of each flexible strip.