Queensland under-19s gun LJ Nonu scored a hat-trick on the wing to stamp the Ipswich junior as a star in the making.
Captain O'Sullivan, playing at No.7, was instrumental in most of the side's six first-half tries as fullback Donoghoe, five-eighth Jake Averillo and hooker Harrison Graham created havoc in the NRL Pre-Season Challenge clash in Cairns.
Dolphins prop Josh Allen, the son of Brisbane and Queensland front-rower Gavin Allen, made a statement in the first 40 minutes that he is an NRL player of the future. Second-rowers Aublix Tawha and James Walsh were also enormous.
O'Sullivan, off-contract at the end of the year, made a compelling claim to be considered for the round-one NRL clash with South Sydney with his organisation, kicking and passing game on-song.
Averillo scored a first-half try with skill and speed, and versatile Fijian international Donoghoe had two try assists and showcased blistering speed .
Nonu, a Queensland under-19 representative, crossed for two first-half tries to give the visitors a 34-4 lead at the break, then scored the first try of the second stanza with brute strength.
New coach Kristian Woolf, who has clearly had a key influence on how the Dolphins played, was in the coaches' box with his assistant Nathan Fien, who had been given oversight of the team for the trial.
Woolf has now got a tougher selection call to make for the NRL season opener after so many of his fringe top-17 players shone.
It was a perplexing and poor night for the Cowboys. Coach Todd Payten will have to write it off as a match where everything went wrong on both sides of the ball.
Second-rower Kai O'Donnell, formerly of Leigh Leopards, was one of their best.
PNG international Robert Derby, who had a tough evening, scored a second-half try with a clinical finish.
