We introduce a novel tuning mechanism based on pressure actuating force, which can enable a broad spectrum of tunable elastomeric optofluidic devices. Thanks to the flexibility of the Polydimethylsiloxane (PDMS) material, the local deformation inside PDMS chip can be generated by filling the compressed air/liquid into the embedded channels. Such tuning method turns out to be very simple for fabrication and control, also being compatible with microfluidic chips. To this end, we have demonstrated the pressure mediated tunable optofluidic gratings, tunable optofluidic laser, and microfluidic 2x2 optical switch.