Seven of the eight institutions composing the Ivy League are older than the United States of America.
Seven of the eight institutions composed of the Ivy League are older than the United States of America.
Seven of the eight institutions composing the Ivy League are older than the United States of America.Seven of the eight institutions composed of the Ivy League are older than the United States of America.
The verb "compose" relates parts to whole. If the parts are the subject, the verb must be active: [parts] compose the [whole]. Here, the individual institutions are the "parts", and the Ivy League is the "whole."