The St George arm of the group is understood to have paid up to £80m for a 7.5 acre site in Hammersmith, which already holds planning permission for 700,000 sq ft of offices and leisure.
Berkeley is also understood to be close to finalising deals to buy for two former Government buildings in the Victoria area.
The new deals come soon after St George boss Tony Carey unexpectedly left the business last month.
Berkeley has refused to comment on the reasons for his departure although people close to the company say there was rumoured to be disagreement about the future direction of the London business.