Middlesex batted first but with Ambrose in excellent form behind the stumps, the wickets soon started to tumble.
Eoin Morgan hit 62 but with Neil Carter taking three wickets and braces for Boyd Rankin, Ant Botha and Jeetan Patel after Chris Woakes had started the ball rolling in his third ball when Ambrose caught Compton, Middlesex crashed to 165 all out.
Neil Carter was also steady with the bat making 56 after Jon Trott had been dismissed for 13. Ian Bell came to the crease and hit an unbeaten sixty which included eight fours whilst Ambrose chipped in with 22 after Jim Throughton had been run out for three, to see Warwicks safely past the total with six wickets in hand.
On Thursday, it is FP Trophy action again for Warwickshire who travel to Taunton to play Somerset. Play starts at 10.45 and then on Saturday, Warwicks travel to Edinburgh to play Scotland at The Citylets Grange.