Hawthorn kicked the last five goals of the game at Windy Hill on Saturday to break open a previously tight contest and win 7.14 (56) to 3.8 (26).
The victory lifted Hawthorn at least temporarily one spot into second above Melbourne, who were scheduled to play at Brisbane later on Saturday.
It was their first AFLW win over the Bombers and a strong response after last week's loss to Port Adelaide.
On a wet afternoon when players had difficulty with shots for goal, McDonagh bagged three majors for the third successive game, boosting her season tally to 19.
She kicked Hawthorn's two first-half goals with classy left-foot finishes, then racked up their first major of the final term, converting a right-foot set shot from close range after taking a mark.
That last effort ensured she matched compatriot Cora Staunton and Katie Brennan in notching 50 AFLW goals in the least amount of games, taking 41 to reach the milestone.
McDonagh also set up two goals for Greta Bodey, who missed three set shots in the first half.
Essendon slumped to an eighth straight loss but looked anything but a 14th-placed team for the first two and a half quarters.
They were level at quarter- and half-time and generated more contested possessions across the game, but couldn't create and finish enough chances.
Co-captain Bonnie Toogood was the chief culprit, kicking 0.4.
Chloe Adams goaled to give Essendon the lead early In the third quarter, but they could only muster a single behind after that.
Hawthorn's Laura Stone kicked a goal from close to 60m and inside the centre square to regain the lead for her side and trigger their decisive surge.
Bodey's double gave the Hawks an 18-point lead at the final change, before McDonagh's third and a goal to Elli Symonds completed a comfortable win after a tough early struggle.
"It was just a bit of a grind, we know that's Essendon's kind of game," McDonagh told Fox.
"They are tough out in the contests and they love to play a quick brand and we had to take our opportunities.
"We missed a few, which we weren't too happy with, but at least we got the win,'' added McDonagh, whose team finish their regular-season commitments against pacesetters North Melbourne on Friday.
Georgia Nanscawen, Georgia Gee and Stephanie Cain were among the best players for the Bombers.