A theory of optical emission of quantum dot arrays in quantum microcavities is developed. The regime of the strong coupling between the quantum dots and photonic mode of the cavity is considered. The quantum dots are modeled as two-level systems. In the low pumping (linear) regime the emission spectra are mainly determined by the superradiant mode where the effective dipoles of the dots oscillate in phase. In the nonlinear regime the superradiant mode is destroyed and the emission spectra are sensitive to the parity of quantum dot number. Further increase in the pumping results in the emission line narrowing being an evidence of the lasing regime.