Southwood, who turned 22 last month, has also signed loan terms which take him back to Scottish Premiership side Hamilton Academical until the end of the current campaign.
At New Douglas Park, Southwood has impressed – breaking into the first team in November and playing eight times in total for the Accies.
His last game for Brian Rice’s men came at the end of 2019, securing a 2-1 win at high-flying Motherwell before returning to the Royals’ ranks to be given a place in the first team squad for our FA Cup Third Round ties against Blackpool.
A product of our Academy, Southwood has previously enjoyed loan spells at Bath and Eastleigh and was a member of England’s Under-20 World Cup-winning squad in South Korea.
With the ink now dry on a new contract at Reading, Southwood returns to South Lanarkshire and could play a part in a top flight encounter with Hibernian on Wednesday night ahead of a return to New Douglas Park for a home clash with Livingston at the weekend.
Everyone at Reading Football Club would like to wish Luke the very best of luck in his loan spell north of the border.