After Ray decided not to seek reelection in 1970, Grant ran in his place and represented District Three in the Texas House of Representatives from January 12, 1971 to January 8, 1981. During his first term, the 62nd Legislature, Grant became a member of the "Dirty Thirty," a group of representatives who "grouped against... state officials charged in a bribery-conspiracy investigation by the United States Securities and Exchange Commission." Grant served nine years as Chairman of the Texas House Judiciary Committee.