Matt Spriegel notched his second half-century in successive days before Northamptonshire staged a disappointing collapse at the start of their Second XI Championship fixture against Middlesex at Radlett.
The County newcomer hit 58 and shared a second-wicket stand worth 79 with Rob Keogh (38) as Northamptonshire reached 99-1 after winning the toss.
But the last nine wickets then tumbled for just 39 runs as the visitors subsided to 138 all out.
Ravi Patel (4-40) and Corey Collymore (4-22) did most of the damage - and the County needed early wickets to get back into the game.
Ollie Stone duly obliged with two successes in an over to reduce Middlesex to 11-2. But opener Adam London (94no) and Tuesday's Trophy centurion Adam Rossington (87no) prevented any further alarms for the hosts, who closed on 198-2 - already 60 runs ahead.