After a short and unsatisfactory period working in the family brewing business, he was able to convince his Quaker parents to allow him to pursue a career in art. He was apprenticed to a wood-engraver, Ebenezer Landells (1808–60), who recognized Foster’s talent for drawing and set him to work designing blocks for engraving. Foster also provided designs for Punch and the Illustrated London News. In 1846 he set up on his own as an illustrator. The rustic vignettes of the seasons that he contributed to the Illustrated London News and its counterpart, the Illustrated London Almanack, established him as a charming interpreter of the English countryside and rural life and led to his employment illustrating similar themes in other publications. During the 1850s his designs were much in demand; he was called upon to illustrate volumes of the poetry of Longfellow, Sir Walter Scott and John Milton. His range was limited, however, and he was criticized for relying on the same rural imagery regardless of the nature of the text.
Foster’s book illustration culminated in Pictures of English Landscapes, commissioned in 1858 by the engravers George Dalziel and Edward Dalziel and published in 1862. Intent on establishing himself as a watercolour painter, he stopped accepting further commissions for book illustrations in 1858. In 1859 he exhibited for the first time at the Society of Painters in Water-Colours in London. His initial bid for membership was rejected, but he became an associate the following year and achieved full membership in 1862. In his watercolours he developed further the themes of an idyllic rural England with which he had made a name for himself as an illustrator. Three characteristic early examples are The Milkmaid (1860; London, V&A), The Hay Rick (1862; New Haven, CT, Yale Centre British Art) and Lane Scene at Hambleden, exhibited at the Society of Painters in Water-Colours in 1863 (London, Tate). His watercolour technique, with its reliance on stippling rather than broad washes, reflects his experience in designing for wood-engraving; but it also suggests an awareness of the watercolour styles of such popular contemporaries as William Henry Hunt and John Frederick Lewis. His work was appreciated as being Pre-Raphaelite in detail, without the harshness of colour and the unorthodox compositional formats that rendered the Pre-Raphaelites’ work disturbing. Foster’s watercolours proved even more popular than his illustrations. Each new work was eagerly awaited. Chromolithographs spread the popularity of his realistic but sanitized rustic images to an audience who could not afford the watercolours.
In 1860 Foster built an elaborate Tudor-style home, known as The Hill, in Witley, Surrey; this became a social centre for a group of artist friends including Fred Walker, Charles Keene and William Quiller Orchardson. Interior decoration was provided by Morris, Marshall, Faulkner & Co. Foster assembled an impressive collection of British art at The Hill, including works by J. M. W. Turner, William Henry Hunt, John Frederick Lewis (The Hareem, 1850; London, V&A), Samuel Palmer and Edward Burne-Jones.
While rural England was the inspiration for much of his work, Foster travelled regularly on the Continent, gleaning material for publications and watercolours. In 1852 he journeyed down the Rhine, seeking subjects to illustrate an edition of Longfellow’s Hyperion. Another tour through Belgium, Germany and Switzerland in 1854 provided material for The Rhine and its Picturesque Scenery,/i> (pub. 1856). In the 1870s he made a number of trips to Italy while engaged on a commission from a Lincoln corn merchant, Charles Seely, for 50 watercolours of Venice. Visits to Brittany resulted in a volume of 35 lithographs published by the artist in 1878.
In 1893 illness forced Foster to sell The Hill together with most of his collection of pictures. He moved to a smaller house in Weybridge, Surrey, where he continued to paint until his death.
Foster is represented in the following collections: Fine Arts Museum, San Francisco; Indianapolis Museum of Art, Indiana; Royal Academy of Arts, London; Art Gallery of New South Wales, Sydney; Beaverbrook Art Gallery, New Brunswick; Cleveland Museum of Art, Ohio; Courtauld Institute of Art, London; Manchester City Art Gallery, UK; Tate Gallery, London; Tyne & Wear Museums, England; Victoria and Albert Museum, London; York Art Gallery, UK, amongst others.