Andy Reid won Monday's Superstock 1000cc race at the opening round of the British Championship at Donington Park.
The Jordanstown rider came home 2.4 seconds ahead of EHA Racing Aprilia team-mate Joe Collier, with Clogher's Keith Farmer third on the Tyco BMW.
Glenn Irwin followed up his sixth place in Superbike race one on Sunday with a seventh spot in Monday's race two.
Michael Laverty was 10th in both races, with Buildbase Suzuki rider Bradley Ray securing victory in the two events.
Ray leads the championship standings with a maximum 50 points, followed by defending champion Shane Byrne on 31 and Dan Linfoot on 29.
Be Wiser Ducati-mounted Irwin lies sixth with 19 points and Laverty, back with the Tyco BMW team for 2018, 10th on 12.
Carrickfergus rider Irwin had suffered back and neck injuries in a practice crash on Saturday but was passed fit to compete.
Reid, who was a double winner in the Superstock 600 class at the same circuit back in 2014, had failed to finish either of Sunday's Superstock races, the 24-year-old crashing out unhurt in both.
"Things didn't go to plan on Sunday but the team pulled together and helped me on to the top step of the podium. This is just a little taster of what's to come in 2018," said Reid after his victory.
Josh Elliott was second and third on Sunday, but could only manage sixth on Monday, while Seeley added a 13th place to his two fifth position finishes on Sunday.
Australian Billy McConnell heads the series on 41 points, with Farmer second on 37 and Reid fifth on 25.
Reid rode for Tyco BMW in several rounds of last season's British Superbike series but suffered a fractured femur in a Silverstone crash.
He made his debut for the Moneymore-based outfit at Snetterton in July, having previously been left without a ride for the season.
Eglinton's David Allingham was seventh in Sunday's Supersport race but improved to fifth in Monday's outing.