The young striker headed home from close range to open the scoring against Hull at the New Den on Saturday. He slid another chance just wide and had another header cleared off the line as the Lions ran out 2-0 winners.
On Tuesday, Harry drilled home the only goal of the game at Portsmouth, a fine strike from the edge of the box at Fratton Park.
Millwall's assistant boss Joe Gallen said afterwards: "He's a very good finisher, very good all-round game and we're thankful to Tottenham for letting us have him."
Steven Caulker kicked-off the weekend's action with another 90-minute stint for Swansea, who suffered a 2-0 loss against Newcastle.
John Bostock was an unused substitute as Swindon beat Morecambe 1-0 in League Two while in Ireland, a rare loss for Oscar Jansson and Shamrock Rovers, who were toppled 5-1 by St Patrick's in the Airtricity League.
Back in the Premier League on Saturday, Steven Pienaar set-up Everton's second goal for Nikica Jelavic as they drew 2-2 against Norwich. Kyle Naughton was a 75th-minute substitute for the Canaries in that game.
Sebastien Bassong was up against former team-mate Peter Crouch - and Crouchy had the final say with the winner as Stoke beat Wolves 2-1.
In the Championship, Andros Townsend was involved in the second goal as Birmingham beat Palace 3-1 while David Button suffered a 4-0 loss for Barnsley against West Ham. Tom Carroll was an unused substitute as Derby drew 0-0 against Ipswich.
Kudus Oyenuga was also an unused substitute as St Johnstone played out a goalless draw against Kilmarnock in the SPL.
In America, Simon Dawkins started and played 52 minutes as San Jose Earthquakes enjoyed a 3-1 win against Vancouver Whitecaps.
Steven Pienaar was on target as Everton beat Sunderland 4-0 at Goodison Park on Monday.
In the Championship, David Button made a couple of key saves as Barnsley picked up a point at promotion-chasing Blackpool.
Andros Townsend was a late substitute as Birmingham drew 3-3 at West Ham and Tom Carroll came on late for Derby as they secured a 2-0 win at Leeds.