Middlesex 177 for 4 (Voges 81*, Simpson 50*) trail Warwickshire 486 for 6 (Chopra 228*) by 309 runs
Warwickshire bagged four wickets for four runs in the space of 10 deliveries to take command of their clash with Middlesex in Uxbridge.
After their acting captain Varun Chopra declared unbeaten on 228 and with his Warwickshire side sitting pretty on 486 for 6, Middlesex crumbled to 28 for 4 before launching a comeback after tea to reach 177 for 4 at the midpoint of the game.
Having fielded in blazing heat for the best part of 10 hours, Middlesex quickly wilted in the face of some impressive new ball bowling by the reigning champion's attack. Dawid Malan fenced at one from left-armer Keith Barker and nicked to third slip then, four balls later, Joe Denly was squared up by a leg-cutter to edge to the same fielder.
Without addition to the total Sam Robson followed a lifting delivery from Chris Wright to pick out Jeetan Patel for a third successive catch at third slip then Neil Dexter feathered Wright's next delivery through to the keeper to go for a first-ball duck.
John Simpson survived Wright's hat-trick ball and, after the tea break, joined forces with Adam Voges to frustrate Warwickshire's bowlers throughout the third session.
Voges, the Australian right-hander, posted a 70-ball 50 with eight fours and went in at stumps on 80 not out, while Simpson reached the landmark from 86 balls and with nine fours in an unbroken fifth-wicket stand of 149. Even so, the hosts will go into day three requiring a further 160 runs to avoid the follow-on.
Warwickshire batted for much of Tuesday's opening two sessions before Chopra's selfless declaration gave them a session and eight overs of day two in which to make inroads into the Middlesex top-order.
Having featured in stands of 113, 113, 55, 100 and 66 Chopra - who was dropped twice on the opening morning before even scoring a run - finally said enough soon after 3pm having batted nine-and-a-half hours for his double century.
When only five short of equalling his career-best 233 (scored for Sri Lanka Premier League side Tamil Union against Sinhalese SSC in Colombo, January 2012) and 14 short of his 1,000th run of the summer, Chopra called time on his marathon stay of 428 balls that led to 20 boundaries.
Resuming on 141, Chopra soon lost his third-wicket partner Ateeq Javid for 22 when he prodded forward to a Corey Collymore delivery only to edge to the keeper. Left-hander Tim Ambrose marched in to add more pep to the innings with a brisk 60 from 78 balls before his push drive against off-spinner Ollie Rayner picked out Malan at short extra cover.
Having gone it at lunch on 388 for 4, Warwickshire promoted Chris Woakes to carry in the impetus Ambrose had given them and he duly obliged with a straight six against Ravi Patel in a cameo 34 that ended when he chipped a return catch to Rayner.
Middlesex dropped their fourth catch of the innings when Rikki Clarke, on 10, saw Joe Denly down a skier at long-on, but only 12 runs later Clarke miscued to cover against Collymore to see Voges pull off a fine over-the-shoulder catch running back toward the rope.
Chopra declared soon after throwing the gauntlet down to his bowlers to extract some response from a, hitherto, extremely placid Park Road pitch - which they duly did.