Crossley was elected to parliament for Lowestoft in 1885, as a Liberal.
In 1886 he joined the Liberal Unionists and held the seat until 1892 when he chose not to stand again for Lowestoft.

In 1897 Crossley stood as a Liberal Unionist in a by-election for Halifax.
He failed that time but stood again in Halifax in the 1900 general election and won the seat.
He was appointed High Sheriff of Suffolk for 1896–97.

Crossley was involved in work regarding the National Coronation gift from the people to their new monarch King Edward VII, and was present as it was awarded to the King two days after the coronation, on 11 August 1902.
For his service, he was invested as a Member (fourth class) of the Royal Victorian Order (MVO).

In August 1902 he was appointed Paymaster General in the Conservative government of Arthur Balfour and was admitted to the Privy Council in December of the same year.
He remained in this post until the government fell in December 1905, and he lost his seat in the 1906 general election that followed shortly after.
Crossley was never to re-enter the House of Commons.

However, in 1916 he was raised to the peerage as Baron Somerleyton, of Somerleyton in the County of Suffolk.
Two years later he was appointed a Lord-in-waiting (government whip) in the coalition government of David Lloyd George.
The coalition fell in 1922, but Somerleyton remained as a whip also in the Conservative administrations of Bonar Law and Stanley Baldwin.
However, after the first Baldwin government fell in 1924, he was never to hold ministerial office again.
Crossley was elected to parliament for Lowestoft in 1885, as a Liberal. In 1886 he joined the Liberal Unionists and held the seat until 1892 when he chose not to stand again for Lowestoft. 
In 1897 Crossley stood as a Liberal Unionist in a by-election for Halifax. He failed that time but stood again in Halifax in the 1900 general election and won the seat. He was appointed High Sheriff of Suffolk for 1896–97.
Crossley was involved in work regarding the National Coronation gift from the people to their new monarch King Edward VII, and was present as it was awarded to the King two days after the coronation, on 11 August 1902. For his service, he was invested as a Member (fourth class) of the Royal Victorian Order (MVO).
In August 1902 he was appointed Paymaster General in the Conservative government of Arthur Balfour and was admitted to the Privy Council in December of the same year. He remained in this post until the government fell in December 1905, and he lost his seat in the 1906 general election that followed shortly after. Crossley was never to re-enter the House of Commons.
However, in 1916 he was raised to the peerage as Baron Somerleyton, of Somerleyton in the County of Suffolk. Two years later he was appointed a Lord-in-waiting (government whip) in the coalition government of David Lloyd George. The coalition fell in 1922, but Somerleyton remained as a whip also in the Conservative administrations of Bonar Law and Stanley Baldwin. However, after the first Baldwin government fell in 1924, he was never to hold ministerial office again.
Savile Crossley, 1st Baron Somerleyton