The paper deals with interpretation of long-periodic (minutes, e.g. < 0.01 Hz) modulations, detected in the microwave records during flaring events on the Sun, as the signatures of large scale transverse oscillations of coronal loops, observed at the same time by TRACE. In the case of transverse large scale oscillatory motions of a loop a properly located observer, besides of the modulation caused by motion of the emission diagram pattern at the main oscillation frequency, may see also a modulation at double frequency of the loop oscillation, resulted by a varying magnetic field during each inclination of the loop, as well as weaker higher harmonics. Identification of such ”modulation pairs” in the dynamic spectra of solar microwave emission and their association with the observed oscillating coronal loops form the major result of the undertaken investigation. Three different events with the detected by TRACE post-flare oscillating loops were considered in that study (Mar.23,2000; Sep.15,2001; Sep.07,2001).