Former deputy Scottish first minister Lord Wallace is to become the UK government's senior Scottish law officer, the BBC understands.
The Lib Dem politician, who played a key role in the coalition talks with the Tories, will return to government as Advocate General for Scotland.
Orkney and Shetland MP Alistair Carmichael is expected to become a senior government whip.
The move means three Scottish Lib Dems now have UK government jobs.
Danny Alexander, one of 11 MPs returned in Scotland after the election, was appointed secretary of state for Scotland.
Lord Wallace, a former MSP and MP in the Northern Isles, previously negotiated deals which saw his party join Labour in coalition government in Scotland.
News of the appointments came as Prime Minister David Cameron was travelling to Scotland for talks with First Minister Alex Salmond.