Dancouga: Super Beast Machine God

Emperor Muge Zarbados and his Empire of Death decide that their next conquest will be the faraway planet of Earth. Muge becomes even more fearsome because of Shapiro Keats, a power-hungry Earthling-turned-traitor. It's up to Shinobu, Sara (Shapiro's old girldfriend), Masato, and Ryo of the Jyusenkitai/Cyber Beast Force to pilot the four Jyusenki/Beast Mecha (Eagle Fighter, Land Cougar, Land Liger, and Big Moth [a mammoth mecha]), which can combine into the giant mech Dancougar.

(Source: Anime News Network)