The young forward, 18, fired home from 30 yards to make it 2-0 in the 13th minute after Andy Keogh opened the scoring early on.
Harry played the full 90 minutes and was denied twice by Doncaster goalkeeper Carl Ikeme as the Lions completed the scoring through Darius Henderson just before the hour.
David Button experienced the other side of football's emotions as Crystal Palace scored a last-minute winner to rob him of a clean sheet on his debut for Barnsley as the Eagles won 1-0 at Selhurst Park.
Andros Townsend played the full 90 as Birmingham suffered a 4-1 defeat at Portsmouth and Tom Carroll came off the bench in the 66th minute as Derby slipped to a 2-0 loss at Brighton.
In League One, Dean Parrett played 69 minutes as Yeovil suffered a 3-0 loss at runaway leaders Charlton.
Steven Caulker impressed again as Swansea toppled Fulham 3-0 at Craven Cottage on Saturday.
The young defender, 20, played another full shift as the Swans dominated at Craven Cottage and ran out deserved winners thanks to two goals from Gylfi Sigurdsson and one from Joe Allen.
It wasn't such good news for Sebastien Bassong as his Wolves side suffered a 5-0 home defeat against Manchester United.
Kyle Naughton also played 90 minutes as Norwich lost 1-0 at Newcastle on Sunday.
In the Championship, Andros Townsend played 79 minutes as Birmingham completed a 3-0 win against Middlesbrough.
Harry Kane was a 79th-minute substitute as Millwall conceded two late penalties to lose 3-2 at home to leaders Southampton. Tom Carroll was an unused substitute as Derby won 2-1 at Doncaster.
In League One, Jonathan Obika started and was then replaced by Spurs team-mate Dean Parrett in the 54th minute as Yeovil came from behind to beat Walsall 2-1 at Huish Park.
Kudus Oyenuga was an unused substitute as St Johnstone beat St Mirren 3-0 in the Scottish Premier League.
Goalkeeper Oscar Jansson made a couple of decent saves for Shamrock Rovers but was then beaten by an awkward bounce at Cork - Shamrock hit back with a last-minute equaliser in the Airtricity League.
In the MLS in America, Simon Dawkins was an unused substitute as San Jose Earthquakes lost 1-0 at home to Houston Dynamo.
Meanwhile, John Bostock has been recalled from his loan spell at Sheffield Wednesday.
The Club can also confirm that it has exercised its option to extend Jermaine Jenas’ contract by a further year until 2014.