An oscillator circuit (10) for generating quadrature-related first and second oscillation signals having equal frequencies comprises a first oscillation circuit (VCO_I) configured to generate the first oscillation signal having a first controllable frequency, a second oscillation circuit (VCO_Q) configured to generate the second oscillation signal having a second controllable frequency; and a controller (100) configured to enable and disable oscillation of the first and second oscillation circuits (VCO_I, VCO_Q) and to control the first and second controllable frequencies, such that when the oscillation is enabled, the first and second controllable frequencies are controlled to be initially unequal and then to become equal.