Members of Congress can count on generous pensions, foreign travel, free medical services, prime parking space and unlimited long distance telephone calls even without the 50 percent pay raise they may soon get.

"The public is usually kept in the dark when it comes to what Congress receives as perks," said consumer advocate Ralph Nader, who listed the fringe benefits in a report.Nader opposes President Reagan's recommendation that members of Congress receive $135,000 in annual pay instead of the current $89,500. The raise will become law unless both houses of Congress defeat the plan by Feb. 8, and House leaders are dropping hints they have no plans to schedule a vote by then.

While lawmakers can't depend on job security, those who stay around a while can live comfortably on their pensions.

Some former members have received over $1 million in pension benefits, and dozens of others are approaching the million-dollar mark, according to Nader's report.

Lawmakers can invest up to 10 percent of their base pay in a 401 (k) pension plan - a program available to many Americans, in which no tax is paid until money is withdrawn.

But for members of Congress, taxpayers match the first 5 percent of salary, a contribution that currently is worth $4,475 a year per member. If the pay raise goes through, the taxpayer share would total $6,750.

Covered by Social Security and - if they choose, the Civil Service retirement programs - members can receive pension benefits at age 50 after 20 years of service or age 60 after 10 years of service.

Lawmakers have shown they love world travel on congressional business. Reports filed by congressional committees and other reports show expenditures of $6.7 million during the 1987 calendar year, money that comes from the State Department budget.

Food and beverage expenses are reimbursed to members when they "discuss matters relating to official duties" with someone other than fellow members or staffers.

Members can participate in federal employee health insurance programs, and they are better off than many Americans if they become ill at work.

The Attending Physicians Service in the Capitol includes doctors, nurses and technicians, and their services include a medical response team; ambulance service; laboratory, X-ray and pharmacy services; immunization and allergy shots. At the Senate Health Club, members can receive free medical testing.

Life insurance of $78,000 is provided for members, with taxpayers picking up half the cost and members paying for the other half.