The 26-year-old has signed a three-year contract at Hillsborough after the Owls and Hornets agreed upon an undisclosed fee.
The midfielder rejoins Wednesday after scoring three goals in 22 appearances while on loan with them last season.
McGugan signed for Watford from Nottingham Forest in 2013, scoring 11 goals in 44 appearances for the Hornets.
Restore Data
| Team | P | W | D | L | F | A | GD | PTS | |
| 1 | Leeds UnitedLeeds | 38 | 23 | 11 | 4 | 76 | 25 | 51 | 80 |
| 2 | Sheffield UnitedSheff Utd | 38 | 25 | 7 | 6 | 53 | 28 | 25 | 80 |
| 3 | Burnley | 38 | 21 | 15 | 2 | 52 | 11 | 41 | 78 |
| 4 | Sunderland | 38 | 19 | 12 | 7 | 55 | 37 | 18 | 69 |
| 5 | Coventry CityCoventry | 38 | 17 | 8 | 13 | 55 | 48 | 7 | 59 |
| 6 | West Bromwich AlbionWest Brom | 38 | 13 | 18 | 7 | 48 | 34 | 14 | 57 |
| 7 | Bristol City | 38 | 14 | 15 | 9 | 49 | 41 | 8 | 57 |
| 8 | Middlesbrough | 38 | 15 | 9 | 14 | 57 | 48 | 9 | 54 |
| 9 | Blackburn RoversBlackburn | 38 | 15 | 7 | 16 | 42 | 40 | 2 | 52 |
| 10 | Watford | 38 | 15 | 7 | 16 | 47 | 51 | -4 | 52 |
| 11 | Millwall | 38 | 13 | 12 | 13 | 37 | 39 | -2 | 51 |
| 12 | Sheffield WednesdaySheff Weds | 38 | 14 | 9 | 15 | 53 | 59 | -6 | 51 |
| 13 | Norwich CityNorwich | 38 | 12 | 13 | 13 | 60 | 54 | 6 | 49 |
| 14 | Preston North EndPreston | 38 | 10 | 17 | 11 | 39 | 44 | -5 | 47 |
| 15 | Queens Park RangersQPR | 38 | 11 | 12 | 15 | 44 | 50 | -6 | 45 |
| 16 | Swansea CitySwansea | 38 | 12 | 8 | 18 | 38 | 49 | -11 | 44 |
| 17 | Portsmouth | 38 | 11 | 9 | 18 | 46 | 61 | -15 | 42 |
| 18 | Oxford UnitedOxford Utd | 38 | 10 | 12 | 16 | 39 | 55 | -16 | 42 |
| 19 | Hull City | 38 | 10 | 11 | 17 | 39 | 47 | -8 | 41 |
| 20 | Stoke CityStoke | 38 | 9 | 12 | 17 | 37 | 51 | -14 | 39 |
| 21 | Cardiff CityCardiff | 38 | 9 | 12 | 17 | 42 | 62 | -20 | 39 |
| 22 | Derby CountyDerby | 38 | 10 | 8 | 20 | 40 | 51 | -11 | 38 |
| 23 | Luton TownLuton | 38 | 9 | 8 | 21 | 34 | 60 | -26 | 35 |
| 24 | Plymouth ArgylePlymouth | 38 | 7 | 12 | 19 | 40 | 77 | -37 | 33 |
| > Championship Full Table | |||||||||
