Few hard facts about this artist's early life are recorded. He is assumed to have been born in Antwerp around 1580 and to have studied under the little-known Andries van Baseroo. He joined the city's Guild of St. Luke in 1602 and married Marguerite Ykens on 8 January 1606. He was also active as a cork merchant. He is believed to have died in Antwerp at the end of 1623 or 1624.
His pupils included Frans van der Borch, Frans Ykens, Paulus Pontius and Jan Willemsen. Beert’s son, Osias Beert the Younger (1622–78), was also a painter but is unlikely to have studied under his father.
Osias Beert is only known as a painter of flowers and fruits. He rarely signed or monogrammed and never dated his work. Since knowledge about this early stage of the Flemish still life is still fragmentary there has been a tendency to attribute too many works to Beert. Osias Beert painted on oak panels, using a glazing technique. By using multiple superimposed layers of very fluid oil he was able to obtain a transparency and a wide variety of colours.
He was one of the first artists to specialize in still life painting when the production of works in this genre was still minor and typically anonymous. His breakfast pieces, usually referred to by their Dutch name ontbijtjes ("little breakfasts"), represent the scene from a high viewpoint with a forced perspective. This technique is commonly seen in early Flemish and Dutch still life painting. His flower still lifes, often showing a vase of flowers in a shallow niche, are reminiscent of the works of Ambrosius Bosschaert.
- Mulders, Christine van. "Beert [Beet, Beirt, Bert], Osias [Osyas], I," Grove Art Online. Oxford University Press, accessed 11 July 2014.
- Osias Beert (I) at the Netherlands Institute for Art History (Dutch)
- Commentaires des chefs- d’oeuvre du musée de Grenoble du XVIe au XIXe siècle (French)
- Vlieghe, Hans (1998). Flemish Art and Architecture, 1585-1700. Pelican history of art. New Haven: Yale University Press. ISBN 0-300-07038-1
- Osias Beert at PubHist