Jim O'Brien's first goal for Motherwell gave them an early lead which looked comfortable until Maguire lashed home a 68th-minute equaliser.
Aberdeen soon had Andrew Considine sent off for a second booking but Motherwell created fewer chances against 10 men than they had against 11, and Dons goalkeeper Jamie Langfield made a brilliant stoppage-time save from Jamie Murphy.
Aberdeen rarely threatened before Maguire added to his two goals in two games for the Under-21s against Albania, but the point leaves them virtually assured of a top-six place as they sit four points ahead of Motherwell and Hibernian.
Motherwell were without injured skipper Stephen Craigan and the suspended Maros Klimpl but they adapted well as Brian McLean filled in well at centre-back.
Aberdeen were without the suspended Mark Kerr while Zander Diamond was absent.
Lee Miller returned after a month out with a hamstring injury but, with Sone Aluko on the bench, there was little service from Aberdeen's five-man midfield before the interval.
Well took control from the start and Steven McGarry had a 30-yard volley saved before O'Brien cut inside and played one-twos with Paul Quinn and David Clarkson before firing a powerful low drive in off Scott Severin.
O'Brien's first goal for Motherwell owed a lot to the deflection but it was just reward for his invention.
Motherwell continued to dominate and gave the Aberdeen defence an uneasy time with some sharp, short passing in the visitors' half.
They survived a 20th-minute scare though when Mark Reynolds appeared to hold Andrew Considine as they challenged for Charlie Mulgrew's free-kick into the penalty box.
Referee Crawford Allan had given a series of soft free-kicks Aberdeen's way but he ignored Considine's penalty claims.
John Sutton had a chance to put Motherwell two up but he sliced the ball 12 yards out after Clarkson's square ball bobbled on the uneven surface.
Graeme Smith was comfortably behind Aberdeen's only first-half effort on target, a 30-yard drive from Derek Young, and Lee Mair escaped with a warning for pulling down Clarkson four minutes after being booked for a foul on the Scotland striker.
Motherwell had more chances before the break. Jamie Langfield held Clarkson's attempted chip and the striker had another shot deflected wide after good movement to meet McLean's clever free-kick.
Stand-in captain Quinn then headed O'Brien's corner wide from eight yards after escaping his marker.
Aluko came on for Mair at half-time as Aberdeen moved to a 4-4-2 and they immediately showed more attacking threat as Smith just beat Miller to the winger's teasing cross.
Motherwell found their feet after a slow start to the half and Clarkson volleyed inches wide from 18 yards after Sutton nodded down O'Brien's cross.
Efforts from McLean and Clarkson sailed not far over and Langfield pushed Stevie Hammell's cross just over his bar.
Smith pushed wide Aluko's powerful strike on a rare foray forward from the Dons but they were soon level.
Miller flicked on Severin's long throw and Maguire turned and blasted it in off the bar from six yards.
Aberdeen's celebrations were soon tempered by a red card for Considine, who clumsily bundled over Clarkson on the touchline less than 15 minutes after being booked for dissent.
Motherwell pushed forward and Sutton's 20-yard drive deflected agonisingly wide off Stephen Hughes.
However, although Sutton had a decent penalty claim rejected when he appeared to be pulled by Mulgrew, they failed to exert any real pressure until injury time.
O'Brien set up two good chances but Langfield brilliantly pushed wide sub Murphy's backward header and Hughes headed wide from 12 yards.