Exterior of office building A Bannockburn, IL office property long-term leased to Shire, part of the 6.8-million-square-foot portfolio Oak Street sold to Stonemont.

ATLANTA—Stonemont Financial Group said Friday it had acquired a net lease portfolio from Chicago-based Oak Street Real Estate Capital for $1.3 billion. The deal, Stonemont’s largest to date, was reported by the Wall Street Journal earlier this week.