Streep will play Mary Louise Wright, the mother of Perry Wright (Alexander Skarsgard), according to The Hollywood Reporter.
Mary Louise Wright is described as a woman who is concerned for the well-being of her grandchildren following her son Perry's death. She arrives in Monterey searching for answers.
HBO announced in December that "Big Little Lies" would return for a second season, with most of the main cast from season one returning. Nicole Kidman and Reese Witherspoon will again executive produce in addition to starring.
"Big Little Lies" premiered on HBO in early 2017 and went on to win eight Primetime Emmy Awards.