Rob Keogh's unbeaten century pressed home Northamptonshire's advantage in the seconds' friendly fixture against the Scotland Development XI at Wantage Road.
Keogh hit exactly 100 not out off 160 balls and shared an unbroken opening stand worth 172 with James Kettleborough (60no) as the County finished the second day's play 245 runs ahead with all their second innings wickets intact.
The Scots were earlier dismissed for 216 in reply to Northamptonshire's 289 all out compiled on the first day.
Paceman Ollie Stone (4-33) and Luke Evans (4-66) did most of the damage with trialist Usman Arif snapping up the other two wickets.
Play begins on Thursday morning at 10.30am.