It's moving time at the Capitol, the game of musical chairs played at the start of every Congress when more than half the members move to new offices.

They move strictly on the basis of seniority and for a variety of reasons -- to get closer to the House and Senate chambers, closer to their committee rooms, to get a room with a view or to get away from a neighbor's dog.

As in most things, the Senate is more deliberate about the process. Moving an estimated 300 House members, including 78 new members, will be completed before Congress convenes Jan. 15. The Senate will take two or three months to move about 40 members.

Congressional corridors are filled with furniture, filing cabinets and carts loaded with office equipment as the moving gets under way. Outside the Cannon Building office of defeated Rep. John Breckenridge (D-Ky.), a painting titled "My Old Kentucky Home" leans against the wall. In a Rayburn building corridor stands a large bas relief map of the world with instructions to ship it home to retiring Rep. Michael Harrington (D-Mass.).

In an effort to bring some order to the chaotic event, House officers asked departing members to vacate their offices by Dec. 15. That provoked some angry refusals by members who said the Constitution makes them representatives of their people until noon on Jan. 3. But most have left or are in the final process of getting out.

Starting just after the November elections, each class of House members, beginning with the most senior class of 1940, was assigned one day to bid for available office space.

On Dec. 7, after all incumbents had been assigned space, the 77 new House members and one new delegate drew numbers from a hat. Rep. Beverly Byron (D-Md.) drew the last number and got an office in the Longworth Building.

The most desirable offices are the three-room suites in the Rayburn building, the home of most major committees. Next most popular is Cannon, the oldest building, which also offers suites of three connected rooms as the result of extensive renovation a decade ago. Longworth offers two-room suites -- with an annex down the hall.

When House members move, they take with them their personal files and office equipment which they bought with their official allowance but leave the furniture behind. Senators take their furniture if they move within one building. If they go across the street they leave their furniture behind.

The House office building superintendent's staff says it can move about 25 offices a day. A member is entitled to have his office painted every two years and when there is a move the empty office is usually painted and the carpet, if worn, is replaced.

House and Senate officials won't put a price tag on the moving game. They say the moving is performed by their own crews and that the offices must be refurbished whether members move or stay put. There is a cost for moving telephones. A congressional district and a Senate office keep the same telephone permanently.

Senators have two or three times more space and equipment than do House members. An official at the Senate Rules Committee, which assigns space, said the operation is well ahead of schedule. All 80 incumbent senators have decided whether to move -- a decision usually not conpleted until February. But Senate office building superintendent J. Lewey Caraway figures the best he can do is move three Senate offices a week.

It has been common in past years to see new senators working in closets or in hall space for weeks waiting for the moving to open up space for them.

Sen. Max Baucus (D-Mont.) was sworn in before Christmas, after his predecessor resigned to give him a little seniority, and moved his gear across the Capitol plaza from House to Senate.

Under current Senate procedures, Baucus could have moved into his predecessor's suite temporarily until permanent quarters were available. But rather than move twice, he is settling permanently into a five-room suite in the most disant corner of the new Senate office building.

It had been occupied by the Indian affairs subcommittee which was moved into an annex building. It lacks some fancy trim and it's a long walk to the Senate floor. But it's more office space than he ever saw before and it's available. CAPTION: Illustration, no caption