Somerset's Lewis Gregory and Craig Overton starred with bat and ball as the MCC continued their impressive showing in the Champion County game in Abu Dhabi, even though their fast bowling colleague Liam Plunkett sat out the day with a sore calf.
In all, 16 wickets fell on the second day, which MCC closed seven down in their second innings with a lead of 298 runs.
Gregory, who had dismissed Sam Robson on the first evening, and Overton took four wickets each on the second day, while their Somerset colleague Jack Leach completed a ten-wicket sweep for the Cidermen.
As on the opening day, wickets fell in clusters as the ball swung extravagantly for periods of the day. After the introduction of Leach did for the nightwatchman, Tom Helm, Gregory produced an inspired spell to take three wickets in eight balls during the afternoon session.
Finding beautiful shape away from the right-handers, Gregory bowled Nick Compton and had Stevie Eskinazi caught behind for a duck either side of Nick Gubbins top-edging a pull straight to the man at midwicket. That left the champions sat perilously on 68-5.
Middlesex’s left-handers Dawid Malan and John Simpson bedded in as batting became easier, putting on a vital stand of 98 to steady the ship. But a superb over, this time from Craig Overton, saw Malan trapped lbw - to a ball that stayed a touch low - and captain James Franklin seen off by a lifting brute to just his second ball.
Before long, Gregory had returned to pick up his fifth wicket, Simpson caught well down the legside by wicketkeeper Ben Cox, then Overton finished the innings with two wickets in two balls - Harry Podmore caught at midwicket and Ravi Patel bowled all ends up. With a lead of 153, Alex Lees, the MCC captain, opted not to enforce the follow-on, in part because of the injury to Plunkett - who will sit out the rest of the match as a precaution.
MCC got off to a flyer in their second innings as Adam Lyth took three fours from Podmore’s first over. But Podmore had his revenge, though, with Lees and Tom Alsop trapped leg before in the space of three balls, the latter recording a pair.
James Harris was soon in on the act, picking up on an encouraging first innings performance, taking a classy diving caught and bowled to get rid of Ben Duckett, then bowling Joe Clarke. Podmore had a third when Ben Cox was trapped lbw.
Lyth kicked on in the company of Gregory before being caught well caught in the deep by Helm off Patel, who Overton then smote for three sixes down the ground.