In 1818, while at Downend, Foster published his "Discourse on Missions". Two volumes of his Broadmead Chapel lectures were published. In 1820, he published his essay "On the Evils of Popular Ignorance", based on a sermon preached on behalf of the British and Foreign School Society in 1818. It speedily went into a second edition, heavily revised. In 1825 he completed an introductory essay to Philip Doddridge's "Rise and Progress of Religion" for the series of "Select Christian Authors" published by William Collins of Glasgow. The period of the missionary controversy brought "Introductory Observations to Dr. Marshman's Statement" (London, 1828).