LAING O'Rourke remains the industry's biggest player in terms of total orders but it is outflanked in the regions by Kier.
Laing O'Rourke raked in £109 million-worth of work in June, including an £85 million job to upgrade a section of the A1 in Northumberland, to strengthen its position in the annual top 50.
With a number of big projects falling out of the firm's annual total in the second half of the year, Ray O'Rourke's empire could soon face competition for the top spot.
Kier is Laing O'Rourke's closest challenger in the annual top 50 after leapfrogging Bovis Lend Lease and Carillion last month.
Kier came fifth in June's monthly table after bagging £88 million-worth of work from a staggering 26 contracts, easily the largest number of contracts won last month and down to Kier's burgeoning network of regional contracting subsidiaries.
The firm's provincial strength has taken Kier to the top in three of the UK's dozen regions in the 12 months to June 2005.
Kier is top in Wales and East Anglia, traditionally two of the smaller regional generators of work, but also in the south-east, one of the most competitive regions.
Excluding Northern Ireland, which remains the province of local contractors, with Gilbert Ash top dog, Kier is among the top firms in eight of the 11 British regions.
Laing O'Rourke came first in the north, ahead of a strong showing from local firm Tolent, and in the north-west, where Bovis Lend Lease ran in second.
In total, Laing O'Rourke featured among the leading firms in seven regions, including Scotland, where Kier also failed to make the top flight and Carillion came first by virtue of its work with News International.
Laing O'Rourke was edged into second place in the south-west, where local firm Midas took top spot, and was not far off the pace in the east Midlands.
National outfit Bowmer & Kirkland, which is based in this region, pipped Norwest Holst to first place.
B&K also turned in a strong performance in the west Midlands, coming second behind Balfour Beatty with Laing O'Rourke just clinging onto a place in the top flight.
Bovis Lend Lease came top in Yorkshire and regional outfit Caddick made the table.