The scrum-half, once on Widnes' books, kicked eight goals and scampered over for the crucial try before half-time as the Jets overcame a brave challenge from the South Norfolk Saints to win 40-12.
The Saints were handicapped at Cheltenham by the absence of half their first-choice players at the wedding of a team-mate, but they still competed fiercely until the last 20 minutes, when Crawley ran away with it with two tries apiece from Mark Henderson and Rod Hammond.
The final score was a poor reward for some outstanding efforts in a pack led by the props Tim Groom - an unfortunate surname in the circumstances - and Ken Dodds.
Dodds ran close to the man-of-the-match award, but there was no denying O'Reilly, who organised his side superbly as well as registering his own 20 points.
Both sides go into next season's Challenge Cup draw, but South Norfolk are determined to make up for this year's disappointment when an expanded Conference kicks off next summer.
"We asked for a 24-hour postponement and there's no doubt that we would have won with a full-strength team," said the Saints' vice-chairman, Jim Collins. "We will be back and we will win it next year."Reuse content