As the Virginia General Assembly was going into the final week of its 1985 session, the last of Democratic Gov. Charles S. Robb's term, the governor took off on a weekend skiing trip in the Blue Ridge Mountains.

And on Saturday, just as the assembly adjourned, Robb used a helicopter to rush back from a national meeting of governors in Washington to receive a traditional delegation of legislators announcing the session's end.

Both trips were symbolic of Robb in transition, mirroring what politicians say is his low-key mastery of Virginia's legislative process -- after a bumpy start in 1982 -- and his widening interest in national politics. He is entering the final months of a four-year term as one of the state's most popular governors.

After Jan. 9, when the 46-day session began, Robb went out of town 15 days. For some of that time, he played a high-profile role in the national Democratic Party, where he led a losing fight to name a moderate chairman of the Democratic National Committee.

Robb also began moving to set up an independent Democratic Leadership Council with other elected Democrats across the country that would speak as a moderate voice in party affairs.

In the process, Robb, the son-in-law of President Johnson, has drawn attention as one of several young party leaders who are potential candidates for president or vice president on the Democrats' 1988 ticket.

While Robb has pursued his national agenda, denying that he has any immediate interest in future public office, he has drawn little complaint from legislators, who say he or his staff were always available for consultation.

"The governor showed he has a very quiet but firm hand on state government," said Henrico County Democratic Del. Ralph L. Axselle Jr. as the 1985 session ended with several legislative victories for Robb. "He's at times accused of being too low-profile, but he pretty much has gotten what he wants."

"His mark on the state is pretty much made," said state Sen. Joseph V. Gartlan Jr. (D-Fairfax), who suggested that there was not much left for the governor to do. "In the 1985 session," he said, "he could only screw up."

The most his critics have said is that Robb brought only a modest agenda before the 140-member legislature this year, for example settling for only minor changes in the state's restrictive voter registration laws after two years of publicity from a commission he appointed.

And Robb shied away from some of the assembly's most controversial issues, declining to get involved in a prolonged fight over a bill that would have restricted the right of unmarried girls under age 18 to have an abortion.

Robb also played no public role in a historic compromise that shifted millions of dollars in state highway money from rural to urban areas. Robb said in his State of the Commonwealth address Jan. 9 that it was time for a change in the formula, but he offered no other advice.

But the legislature made only minor changes in nearly $300 million of new spending proposed by Robb, funds that went to favorite projects such as education and economic development.

"The budget was far from modest," said George M. Stoddart, Robb's press secretary. "It was a major change, and it was the governor's highest priority." Stoddart said that all the bills on issues Robb had mentioned in his State of the Commonwealth address had passed the legislature.

Of 73 measures backed by Robb, some just housekeeping changes in the state's operations, only three were rejected.

"The way we get our work accomplished is in private meetings with legislators," said Philip Abraham, a Robb policy adviser. "If we do our job right, you don't see us, but we get the votes." Abraham was one of 15 staff aides who met each morning during the session to track Robb's legislation and keep him abreast of the assembly's sometimes quickly changing mood.

The legislature also approved Robb's proposal to extend the rights of handicapped persons against housing and employment discrimination, a bill bitterly opposed by business interests. It also approved raising the legal drinking age for beer to 21 over the next two years, a measure Robb last supported in 1983.

The legislature gave him patronage power over 500 agency management jobs now protected by the state's civil service, a measure prompted in part by the state's inability to fire some mental health and corrections system employes.

Robb's administration has been embarrassed by nearly a year-long series of escapes and inmate disturbances and a controversy over an employe's wiretapping of lawyers and their inmate clients.

Robb moved quickly in the session to provide funds to beef up security and management of the state's prisons, in part to get a handle on the issue that he called his "number one problem" and to blunt Republican criticism certain to be heard in this falls's House and statewide elections.

"The budget backed up" his promise of changes, said Stoddart, and at least for the session, "the issue died."

State Sen. Edward E. Willey (D-Richmond), chairman of the powerful Finance Committee, agreed.

"No matter how much or how little you do, things like prisons and mental [health] come up every 10 years or so," he said. "It doesn't matter who the governor is, whether it's Chuck Robb or George Washington."