What were the T rexes most fond of eating back in the time of dinosaurs?

T. Rex was a carnivore that fed on hadrosaurs, ceratopsians, ankylosaurs, sauropods, and other dinosaurs living in the late Cretaceous. There is some evidence that it was a scavenger, similar to a hyena today.

Compsognathus. Chicken nuggets for tyrannosaurus