Rep. Patricia Schroeder (D-Colo.) introduced legislation yesterday that would kill the Reagan administration plan to make it tougher for U.S. workers to get longevity pay raises and reduce layoff protection for senior workers.

Schroeder's bill would not allow the White House to administratively make changes in federal pay, layoff and collective bargaining practices.

Two weeks ago the White House proposed that within-grade pay raises, which now are virtually automatic for white collar employes, be linked to performance. It also wants to revamp layoff rules to give greater job protection to employes based on their performance rather than their seniority.

The administration plan also would limit issues that government and unions can take up in collective bargaining and change overtime pay rules.

Administration officials hope to put the sweeping personnel changes into effect by October.

Making employes get a better-than-satisfactory job rating to qualify for in-grade raises, which are worth about 3 percent, would affect all of the government's million-plus white collar workers.

Workers come up for an in-grade raise (in addition to any general pay increase) every one, two or three years depending on their time in grade. The government says the present "easy" qualification requirements result in in-grade raises for 99 percent of employes who come due for them.

The layoff changes would give less job protection to employes with long service, and more to those with top ratings from their bosses. Since the Reagan administration took office, about 3,000 Washington area feds have been layed off under the last-hired-first-fired principle the proposals would change.

Administration officials argue that the changes, emphasizing performance in pay and job security, will simply introduce good private sector management practices into the government.

Opponents--many federal workers, all their unions and Schroeder--contend that the changes are designed to give political appointees a strangle hold over the career civil service.

President Reagan would almost certainly veto the Schroeder bill if it got to his desk. The apparent strategy, however, is to get support for the bill on Capitol Hill and then have it attached as a rider to a piece of legislation that the president has to sign.

RIF Rules Change: Persons opposed to the proposed layoff rules changes have until May 31 to get their comments in to the Office of Personnel Management.

When the proposals were published in the Federal Register, the public was told there were 60 days to comment on items dealing with longevity pay raises and new collective bargaining guidelines for unions. But the layoff rules had only a 30-day comment period. OPM says that was a mistake, and that the deadline for all comments, on all the items, is May 31.

Administration officials will be asked to explain--and justify--the complicated and controversial changes in hearings next Wednesday called by the Senate civil service subcommittee.

Among other things the unit, headed by Sen. Ted Stevens (R-Alaska), wants to know if the proposed layoff guidelines will strip any job protection from veterans.