Frequency response of an oscillator

You may want to ask for a clear question (or retell the question exactly).

Oscillators are autonomous circuits, they don't have any frequency response..

If it's a Voltage controlled oscillator, then try plotting tuning frequency vs control voltage.

Any oscillator which can be tuned has a specific frequency response. This means that the output power is not constant over frequency. VCOs are special oscillators designed for tunability over a specified bandwidth. Their output power should stay within specified limits when the frequency is tuned by control voltage.Such VCOs also can have a "second" frequency response meaning how fast their frequency can be tuned by the control voltage.

In oscillator analysis there is a method named "Open-Loop Charaterization" where the circuit considers the characteristics of the cascade open-loop amplifier rather than as an oscillator.

From R. Rhea "Discrete Oscillator Design" see the attached example of an open-loop amplifier frequency characteristics.
In fact the entire book is pointed to this kind of oscillator analysis.

So, you have to understand how your oscillator works, and brake the feedback loop, making it working as an amplifier.

Yes - I agree to vfone`s answer.
Most probably, it is the LOOP GAIN that is to be plotted because it is used to check the oscillation condition (Loop gain=unity and real at f=fo only).

So we finally got three possible interpretations of "oscillator requency response". Each of them applies only to a certain class of oscillators, e.g. the loop gain characteristic only to a feedback loop oscillator, not to a negative impedance based type. We could really avoid much guessing by a clear question.