Three other inmates are accused of roles in the drug ring.
One inmate was described by the FBI agent as a facilitator who used contraband cellphones to “have individuals deliver stuff to other individuals.”
Garcia is facing a separate state assault and conspiracy case that accuses him of ordering the shooting of another inmate's son.
Oklahoma City police reported the gunmen shot a 13-year-old boy and the boy's mother by mistake.
Both victims survived the January attack.
An informant told police that Garcia and two other SUR Movement gang leaders ordered the shooting during “a three-way phone call” from prison, according to a police affidavit.
Garcia has pleaded not guilty to the state case.