Northland lost both batsman in quick succession but another solid partnership between Neal Parlane (59) and Matt Taylor (58) helped Northland to a commanding 336 all out.
Northland got off to the best possible start as Northern Districts bowler Brett Randell (2 for 31) knocked off Bay of Plenty captain Peter Drysdale (2) and Joe Carter (0) in quick succession.
Tom MacRury (60) and Sean Davey (42) consolidated but three quick breakthroughs from Cooper (4 for 71) and Caleb Boswell-Smith (1 for 31) put Northland back in control.
The next couple of hours were a slog as Jono Boult (81), Ben Musgrave (22) and Tim Clarke (67) inched Bay of Plenty closer to the first innings target.
However Cooper, backing up from a pair of Northern Districts first-class appearances, took the wickets of Boult and Musgrave to give Northland the edge.
Tom Herman (3 for 37) came back to the bowling crease and knocked over the last three wickets in a five-over spurt to end Bay of Plenty's innings at 317, giving Northland the points.
Northland next travel to take on Hamilton, who lost on first innings by 330 runs to Counties-Manukau, on November 25-26.
Northland 336 (Ben Hyde 71, Brad Kneebone 61, Neal Parlane 59, Matt Taylor 58, James Blackett 2/20) Bay of Plenty 317 (Jono Boult 81, Tim Clarke 67, Tom MacRury 60, Henry Cooper 4/71, Tom Herman 3/34).