Mellor are now fifth in the Premiership, but only two points behind second placed Bedians, who visit Wood Lane next Saturday.
With manager Si Dalby away, assistant Phil McGreal selected Dan Byrne at left back, switching Dave Whelan to right back. Paul Swann, returning from a hernia, was a welcome sight on the bench.
There was drama inside 30 seconds when a back pass was shanked up in the air by Grove's keeper and Matt Cotton came in to head past him into the empty net.
Matt Cotton scores inside 30 seconds
Grove forced a corner on four minutes after a shot was blocked.
On eight minutes Chris Coram fired straight at the keeper.
Mellor were dominating the play but keeper Tom Fletcher was called on to palm a shot away after 14 minutes.
On 23 minutes a Craig Frisby clearance found Matt Cotton who danced inside two tackles and slipped the ball to the right to Matt Jamieson whose curling shot found the net for 2-0 off the post to the keeper's right.
Matt Jamieson makes it 2-0
Cotton tested the Grove keeper on 25 minutes and 40 minutes.
Mellor were dominant, Jonny Cooke a threat on the right and Cotton and Jamieson giving the Grove defenders plenty to think about.
The second half began with a flowing Mellor move between Jamieson, Jonny Cooke and Chris Coram who set up Jack Parr but his carefully prepared shot was a foot wide.
Jack Parr scores Mellor's third
Parr made amends, however, on 56 minutes sliding in from 12 yards after Dan Byrne had released Matt Cotton who unselfishly crossed for the midfielder to net from 10 yards.
Carl Brindley slams in number six
That was Parr's last contribution and he was immediately replaced by Rob White who went to full back, releasing Dave Whelan to right midfield.
On 59 minutes following a poor goal kick, White intercepted and played the ball forward to Cotton who hooked the ball in for 4-0.
On 62 minutes Carl Brindley replaced Matt Cotton
On 74 minutes Dan Byrne got on the scoresheet, firing home after Chris Coram's shot was blocked.
Then three minutes later Brindley made it 6-0 after another Coram shot was blocked.
Paul Swann replaced Jonny Cooke, who had tormented Grove's right flank all afternoon.
On 87 minutes Swann fed Dave Whelan who found Matt Jamieson and the striker thumped home number seven.
On 90 minutes Whelan had a long range shot well saved.
Then in injury time a lovely move between Whelan and Rob White saw the full back cross only for Carl Brindley's shot to be blocked.
Ben Beer was named Man of the Match but Dan Byrne was not far behind.
Mellor Seconds lost 2-3 at home to Moorside Rangers.
Mellor wnt 0-2 down and then missed a penalty.
The visitors went 0-3 ahead but Mellor rallied with goals from Scott Cassidy and Carl Bradbury.
Matt McNulty was Man of the Match.
The Thirds, well placed in third spot in Division C, beat Whalley Range Third away 6-2. Man of the Match Marcus McNulty scored three, Nick Entwistle (2) and Sam Healey also scored.
The Fourths lost 1-2 against Hooley Bridge Thirds. Thomas Tognarelli scored. Mike White was Man of the Match.