Middlesex138 and 123 for 6 (Beard 3-17) lead Essex 236 (Wheater 83*, Andersson 4-38) by 25 runs
Fast bowler Beard took three wickets in 21 balls after tea to leave Middlesex with their backs against the wall at the Cloudfm County Ground, Chelmsford. The visitors did tiptoe into a lead but having ended the day on 123 for 6, ahead by 25, they'll need an extraordinary effort from the tail to set Essex a tricky fourth-innings chase.
Earlier, Wheater posted a three-year high score to give Essex a commanding first-innings lead of 98, as they pocketed four bonus points.
After 15 wickets had fallen on the opening day at the Cloudfm County Ground, Chelmsford, batting seemed much easier for the most part on the day two. Wheater used the friendlier conditions to his advantage with a mature innings, partnered well by Ryan ten Doeschate and Simon Harmer.
The home side's morning, in which they lost just three wickets, was spoiled slightly by a back spasm suffered by ten Doeschate. The former captain had seemingly run an innocuous single unharmed, but felt a problem while scratching out his guard.
He needed five minutes of treatment on the pitch before retiring hurt on 31, having put on 35 with Wheater.
Harmer continued with Wheater and took Essex to a potentially valuable batting point. It added to their three bowling points from the first day, and with Derbyshire's batting woes, could be an important factor in the race to secure a place in the final at Lord's later this month.
Wheater, who hasn't scored a County Championship century since returning from a stint at Hampshire in 2016, cruised to his fifty in 76 balls. He and allrounder Harmer put on 72 before Harmer was lbw - the first of three quick wickets for Martin Andersson.
The fast bowler then had Beard and Sam Cook caught in the slips in the 62nd over to bring ten Doeschate back to the crease, albeit with Dan Lawrence as his runner. The 40-year-old, who didn't field, added 12 more runs to his tally before he departed to hand Andersson a fourth - returning figures of 4 for 38.
Jamie Porter was the final man to go, caught behind off Tim Murtagh, to leave Wheater stranded on his highest first-class county score since he reached 88 versus Somerset in August 2017.
All eyes were now on the Bob Willis Trophy's leading wicket-taker Harmer and whether he could spin his usual magic. Instead it was the seamers, in particular Beard, who took centre stage from the Hayes Close End by bowling incessant line and length.
Sam Cook pocketed an early scalp as Sam Robson, on likely his final innings of the summer, pushed to Harmer at second slip. Offspinner Harmer, who was a threat throughout his 21 overs, then picked up Nick Gubbins leg before on the cusp of tea.
When Beard entered the attack he found pace to accompany accuracy, demonstrated perfectly by sending Steve Eskinazi's off stump catapulting with a beautiful delivery which straightened.
Max Holden had provided a rear-guard with 37, which included a pulled six off Porter, but became Beard's second victim when he also lost his off-peg. Middlesex, still in arrears, were then 84 for 5 when a driving Andersson edged Beard to second slip.
John Simpson and former Essex loanee Robbie White took their side into the lead with a 38-run partnership. But Harmer returned for a second spell to pin White leg-before to set up a likely three-day finish.