We are given two tangents \( TP \) and \( TQ \) drawn from an external point \( T \) to the circle, and we know that the angle \( \angle POQ = 120^\circ \).
The key property here is that the angle between two tangents from a common external point to a circle is equal to half the angle subtended by the chord joining the points of tangency at the center of the circle.
Thus, the angle \( \angle OTP \) is:
\[
\angle OTP = \frac{1}{2} \times \angle POQ = \frac{1}{2} \times 120^\circ = 60^\circ.
\]
Therefore, the value of \( \angle OTP \) is \( \boxed{60^\circ} \).