The company expects to invest a six-figure sum extending its round the clock IT support function and has also added further storage at its data centre in Edinburgh.
Staff numbers in Scotland – where around 40% of the group's £19 million turnover is generated – have increased by more than 20% to 44 in the past 12 months as a result of securing deals with clients such as Edinburgh Airport and Balfour Beatty Engineering Services.
It is also looking at potential locations across central Scotland for the location of a third data centre.
Hugh Gillen, Onyx Group director, said: "We have filled three of the five data halls in Edinburgh and are on to expanding our fourth this year.
"We are also nearing capacity in Glasgow so we are looking at other sites and have been doing homework on that. We are looking to do a further expansion of the Edinburgh site by the end of March and then after that looking at acquisition of a new site.
"With the growth we are experiencing in Scotland we will need to add to what we have between the middle and end of the year so we can have that extra capacity going into 2014."
The company – which has its headquarters in Stockton-on-Tees plus offices in London and Gateshead – runs five data centres and six workplace recovery centres across the UK employing more than 130 people in total.