Twenty-two senators yesterday urged Majority Leader Howard H. Baker Jr. (R-Tenn.) to expedite consideration of legislation reauthorizing the U.S. Commission on Civil Rights rather than leave it to a Judiciary subcommittee chaired by Sen. Orrin G. Hatch (R-Utah), where it could be held hostage.

Hatch has indicated that he won't move a separate reauthorization bill until the Senate votes on three new Reagan nominees to the panel. Some liberals and moderates had threatened to block the nominations.

The panel was set up in the 1950s to monitor progress on civil rights issues, and has been authorized at five-year intervals since. Its present members have sharply criticized Reagan administration civil rights policies. Its current authorization expires Sept. 30.

The letter to Baker, organized by Sens. Charles McC. Mathias Jr. (R-Md.), Joseph R. Biden (D-Del.), Edward M. Kennedy (D-Mass.) and Howard M. Metzenbaum (D-Ohio), notes that the expiration date falls only 15 workdays after the Senate reopened for business this week. "The tight deadline is especially troubling," they wrote, "given the reported intention of Hatch to defer action until senators vote on the pending nominees . . . . If the commission is to survive, we must proceed directly to take up" a House-approved reauthorization bill.

Opponents charge that by replacing three more of the six commissioners--President Reagan has already appointed two others--the administration would undermine the panel's independence. Reagan supporters say he is within his rights to replace commissioners.