Eastern Suburbs bowlers and fielders backed up what turned out to be a match-winning 146 by Trent Park to record a break-through 49-run win against the previously unbeaten City United.
It was the young Griffins' most consistent and prolonged effort against a quality opponent in a number of seasons and cements their spot in the top four.
"That's the best win we've had as a club in the whole time I've been here," Easts skipper Jack Bennett who switched to the Griffins at the beginning of the 2017-18 season said.
"We put in two full days of work to come out winners, it was unreal.
"Everyone dug in for 80 overs plus today in the field today and last week Trent set it up with a big knock.
"We bowled to a plan all day and kept it tight and come away winners, I can't be happier."
Play was held up for about 30 minutes by a break for lightning and City resumed with five wickets in hand needing 90 runs and given their recent record over Easts still slight favourites.
"I think one of the things that was so impressive was that previously we would get ourselves in that position of having them five down, but folded when one of their key batsman like Matt Trappel, Nick Bower or Matt Latham got hold of us," Bennett said.
"Matt Trappel (69) and Latham (57) both got good starts and we were able to get them out and we knocked Nick (7) over early which we were wrapped about as he has destroyed us a few times in the past.
"But we went about it as a team and sticking to the game plan.
"We bowled tight all day and everyone went at under-three an over, which here at East Maitland Park is really impressive.
"It enabled us to prolong the game to go to a second new ball and it proved crucial in the end in getting those last few wickets.
"We bowled to the plan and really dried them up for runs. Trent (Park) bowled 10 overs for 17, (Josh Hicks) Hicksy bowled 35 overs for 80 at East Maitland Park those are fantastic figures.
"Will (Stoneman) bowled a very crucial spell just before the new ball to get Matt Trappel out, which was critical as Matt was in for the long-haul and is very hard to dislodge.
"Cal (Sargent) then used the new ball really well to pick up three wickets."
Northern Suburbs survived a tense final session to hand Raymond Terrace their first loss of the season.
Norths spinning all-rounders Sean Gibson and Jordan Callinan were unbeaten on 29 and 16 respectively as the took their side to 7/212 chasing the Lions' total of 211.
Gibson and Callinan took the score from 166 after Caleb Daskalovski was out for 32.
Dylan Rumble finished with 5/20 as Kurri Weston routed Tenambit Morpeth for just 89 at Morpeth. The Bulls had resumed at 2/39 chasing the Warriors' 177.
In the final game, Aaron Mahony scored his third 50 of the first grade summer as Wests chased down Thornton total of 185 at Thornton Park.