Kevin McDonald was the first to sign, joining on a month's loan from Championship rivals Burnley.
McDonald, 21, is an attacking midfielder who cost the Clarets £500,000 when they signed him from Dundee two years ago.
Paris Cowan-Hall was the second player to sign, having been on trial over the past two weeks.
The forward, 20, had been a free agent since the summer when he was released by Portsmouth following their relegation to the Championship.