Kopelman, 34, popped the question in Sun Valley, Idaho around the holidays, according to the insider.

An art consultant and son of the former CEO of Chanel, Arie Kopelman, Will first stepped out with the "Going the Distance" actress, 36, in February of last year. (According to a source, the couple dated briefly in 2010 but split up at the time, reuniting the following year.)

And, indeed, back in October, a Barrymore pal told Us that the former child star was "yearning to get married and have kids," with Kopelman poised to propose "around the one-year mark of their dating."
Slideshow: Drew Barrymore: Hollywood wild child (on this page)
"He's madly in love and knows she's The One," the insider said of her handsome guy; Barrymore's recent exes include fellow actor Justin Long and The Strokes drummer Fabrizio Moretti.

It will be the third walk down the aisle for Barrymore, who wed Welsh bar owner Jeremy Thomas in March 1994 -- only to split just a month later. Her second marriage, to comic Tom Green, was similarly short lived: They wed in July 2001, and Green filed for divorce that December.