He supported the Parliamentary cause in the English Civil War.
[2] Grey was commander of parliamentarian forces in the east in 1642.
He was speaker of House of Lords in 1643 and was one of the Lay Assessors at the Westminster Assembly from 1643 to 1649.
In 1648 he was appointed a commissioner of great seal but refused the engagement in 1649.
[2] His daughter Katherine married Sir Edward Mosley, 2nd Baronet.