The amateurs took the lead within two minutes with what was the best try of the night. John McAtee, who looked to be on his way to a sparkling professional career with St Helens, jinked through and provided the scoring pass for Paul Raftery, with Dean Pickup adding the goal points.
Oldham, now in exile at Rochdale, hit back with two tries engineered by the scrum-half Daniel Brown running the ball on the last tackle. He initiated the move that ended with Adrian Mead scoring in the corner, before dummying his way over himself.
With two goals from the newly-signed Frenchman, Laurent Minut, Oldham were six points up, although they had to withstand concerted pressure from the amateurs before half-time.
With McAtee off the field, however, all Eccles could manage was a drop goal from Pickup and that was never quite enough.
Oldham's extra strength and fitness began to tell after the break with Mike Prescott taking Emerson Jackman's pass to go over and Jason Clegg wrestling his way in from close range.
Eccles refused to crumble and came close to a reply through the nippy and resourceful Craig Evans. However, they could not narrow the gap, and Paul Crook's well-placed kick gave Mead his second try to make Oldham's victory look more comfortable than it was.
They will have to sharpen up considerably if they are to thrive in the First Division programme that starts this weekend, while Eccles can be proud of their efforts.
Oldham: Minut, Mead, Leuila, Bostock, McNicholas, Crook, Brown, Casey, Hough, Clegg, Shaw, Coulter, Jackman. Substitutes used: Round, Peralta, Prescott, Perrett.
Eccles: Hedgecock, Davenport, Morley, Campbell, Bateman, Pickup, McAtee, Allinson, Billingham, McPherson, Raftery, P Smith, Viller. Substitutes used: Evans, C Smith, Hill, Switzer.
Referee: S Cummings (Widnes).
n Wendell Sailor is heading back to Australia having enjoyed his rugby union experience - but he is still keen to return to league. The big Queenslander collected 15 tries in 13 appearances for Leeds Tykes, ending his three- month spell with the Premiership Two club in their 49-0 trouncing by Leicester at Welford Road on Saturday. "I have really enjoyed my introduction to rugby union. I've managed to score a few tries and the next step is to play in the First Division," Sailor said after the Leicester match.Reuse content