President Reagan will spend the better part of the next four weeks away from the White House, starting Friday when he departs for a 10-day vacation at his California ranch. He'll be back for the last two weeks in April, but then leaves for 10 days in Europe.

Look for Reagan to spend a lot more time in Santa Barbara during this term; five trips there are expected each year. Word at the White House is that Reagan would like to take a long summer vacation -- all of August. He also may spend a week there around July 4.

Now that Reagan has been reelected, it's clear that his aides don't fret as much about the appearance of all these retreats to Rancho del Cielo. They appear to be taking their cue from the boss. ON THE MOVE . . .

Key assistants to Office of Management and Budget Director David A. Stockman are moving on to new jobs.

Frederick N. Khedouri, who was on Stockman's congressional staff and became associate OMB director for natural resources, energy and science, is deputy chief of staff and policy director for Vice President Bush. His successor at OMB is Randall Davis, who was on the staff of the House Energy and Commerce Committee when Stockman was a House member and more recently worked in the White House Office of Policy Development.

David Gerson, associate OMB director for operations and communications, who also worked for Stockman on the Hill, has left for a public affairs job at General Motors. He won't be replaced, but OMB spokesman Edwin L. Dale Jr. will pick up some of his duties. ON THE PHONE . . .

There's no busier press office in town than the one at the White House, where as many as 1,000 calls and hundreds of reporters come each day. Spokesman Larry Speakes is bringing in fresh troops to replace those who have left the pressure-cooker environment for less frantic assignments.

Albert R. (Rusty) Brashear will be deputy press secretary for domestic affairs, replacing Marlin M. Fitzwater, who has become press secretary to Bush. Brashear was a spokesman at the Environmental Protection Agency during some of its most difficult days in 1983 and earned the respect of many reporters at the time. He later served as spokesman for former Interior secretary William P. Clark.

Dale A. Petroskey will become assistant press secretary, succeeding C. Anson Franklin, who went to the Energy Department. Petroskey is administrative assistant to Rep. William F. Goodling (R-Pa.) and was press secretary and campaign manager for Rep. Mark D. Siljander (R-Mich.) Petroskey will oversee the day-to-day operations of the "lower press office," which handles initial queries to the White House and the blizzard of paper work issued each day.

Denny Brisley has taken over the job of coordinating administration television interviews from Kim Hoggard, who has gone to the Treasury Department. Brisley previously worked for Dale at the OMB.

Mary Kayne Heinze comes over from the White House correspondence unit to help answer the telephone calls. She worked on the 1980 Reagan campaign and inaugural staffs and at the Republican National Committee before coming to the White House.