An interior rearview mirror assembly (10, 110) for a vehicle, said interior rearview mirror assembly (10, 110) comprising: a mirror head comprising a mirror casing (12, 112) and a mirror reflective element; a mirror mounting structure configured to adjustably mount said mirror head at an interior portion of a vehicle equipped with said interior rearview mirror assembly (10, 110); a garage door opening module (18, 118) comprising a housing that houses (i) garage door opener circuitry operable under rolling code and (ii) a radio frequency transmitter; and wherein said garage door opening module (18, 118) is operable to wirelessly transmit a radio frequency signal responsive to actuation of at least one user input; a receiving portion (12a, 112a) for receiving a garage door opening module (18, 118) at least partially thereat; and wherein said garage door opening module (18, 118) is releasable from said interior rearview mirror assembly (10, 110); characterized in that, said garage door opening module comprises a portable self-contained garage door opening module; wherein said portable self-contained garage door opening module (18, 118) comprises at least one user input for actuating or controlling circuitry of the module, and wherein the housing of the module houses (iii) a battery for electrically powering said circuitry, and wherein said portable self-contained garage door opening module (18, 118) is operable to wirelessly transmit a radio frequency signal responsive to actuation of said at least one user input of said portable self-contained garage door opening module; wherein, with said portable self-contained garage door opening module (18, 118) at least partially received at said receiving portion (12a, 112a) of said interior rearview mirror assembly (10, 110), said at least one user input is accessible by a driver of the equipped vehicle; wherein said portable self-contained garage door opening module (18, 118) is configured to cooperate with said receiving portion (12a, 112a) to releasably secure said portable self-contained garage door opening module (18, 118) at said interior rearview mirror assembly (10, 110), wherein a cover element (120, 120') is configured to attach at said receiving portion (12a, 112a) to releasably secure said portable self-contained garage door opening module at said receiving portion (12a, 112a); and wherein said cover element (120, 120') is configured to receive light from a light source within said interior rearview mirror assembly (10, 110) and wherein, when said light source is activated, said cover element (120, 120') is illuminated. a mirror head comprising a mirror casing (12, 112) and a mirror reflective element; a mirror mounting structure configured to adjustably mount said mirror head at an interior portion of a vehicle equipped with said interior rearview mirror assembly (10, 110); a garage door opening module (18, 118) comprising a housing that houses (i) garage door opener circuitry operable under rolling code and (ii) a radio frequency transmitter; and wherein said garage door opening module (18, 118) is operable to wirelessly transmit a radio frequency signal responsive to actuation of at least one user input; a receiving portion (12a, 112a) for receiving a garage door opening module (18, 118) at least partially thereat; and wherein said garage door opening module (18, 118) is releasable from said interior rearview mirror assembly (10, 110); characterized in that, said garage door opening module comprises a portable self-contained garage door opening module; wherein said portable self-contained garage door opening module (18, 118) comprises at least one user input for actuating or controlling circuitry of the module, and wherein the housing of the module houses (iii) a battery for electrically powering said circuitry, and wherein said portable self-contained garage door opening module (18, 118) is operable to wirelessly transmit a radio frequency signal responsive to actuation of said at least one user input of said portable self-contained garage door opening module; wherein, with said portable self-contained garage door opening module (18, 118) at least partially received at said receiving portion (12a, 112a) of said interior rearview mirror assembly (10, 110), said at least one user input is accessible by a driver of the equipped vehicle; wherein said portable self-contained garage door opening module (18, 118) is configured to cooperate with said receiving portion (12a, 112a) to releasably secure said portable self-contained garage door opening module (18, 118) at said interior rearview mirror assembly (10, 110), wherein a cover element (120, 120') is configured to attach at said receiving portion (12a, 112a) to releasably secure said portable self-contained garage door opening module at said receiving portion (12a, 112a); and wherein said cover element (120, 120') is configured to receive light from a light source within said interior rearview mirror assembly (10, 110) and wherein, when said light source is activated, said cover element (120, 120') is illuminated.