David Cross and Amber Tamblyn
Steven A Henry/WireImage
08/17/2011 at 05:00 PM EDT
and his longtime girlfriend, Amber Tamblyn, are engaged to be married, her rep confirms to PEOPLE.
The actress, 28 – who starred in General Hospital
and Joan of Arcadia
before moving on to the big screen in the 2005 hit The Sisterhood of the Traveling Pants
– recently returned to TV with a role on House
Cross, 47, is perhaps best known for his outrageousness on the 2003-06 cult sitcom Arrested Development
, on which he played the gaffe-prone, madcap Tobias Fünke. Talk of a feature movie based on the show has long been circulating. Currently, he stars in the British-American comedy TV series The Increasingly Poor Decisions of Todd Margaret
Earlier this month, the couple were spotted
on the patio at Oscar's Cerveteca in Venice, Calif., where they met friends for drinks – beer for him, rosé for her – and casual conversation.