Actively controllable dispersion in on-chip photonic devices is challenging to implement compared with free space optical components where mechanical degrees of freedom can be employed.Here, we present a method by which continuously tunable group delay control is achieved by viseart etendu cashmerie modulating the refractive index profile of a silicon Bragg grating using thermo-optic effects.A simple thermal heater element is used to create tunable thermal gradients along the grating length, inducing chirped group delay profiles.Both effective blue and red chirp are realised using a single on-chip device over nanometre soderhamn ottoman cover scale bandwidths.Group delay slopes are continuously tunable over a few ps/nm range from red to blue chirp, compatible with on-chip dispersion compensation for telecommunications picosecond pulse systems.