opamp output voltage
The opamp is wired in an inverting configuration. 
The output will attempt to drive the inverting input to match the non-inverting input so that the voltage difference between them is zero.
At t = 0 \$ V_+ = 0 \$ so \$ V_- = 0 \$. This means that \$ V_{OUT} = 0 \$ too.
If the question is how does the opamp recover from saturation at power-up then we don't have enough information. As an approximation we can say that it immediately drops to zero.