A bill to raise the state's legal drinking age to 21 won swift and unanimous approval today from a key House committee, sending one of the year's most popular issues to the full House for final action before the session was three weeks old.

House leaders said they hope to move the measure quickly to the floor for a final vote before the momentum fades.

Meanwhile, the Senate panel considering the same measure today heard parents, educators, police officers and members of the governor's task force on drunk driving all plead for the same 21-year-old drinking age as the way to reduce alcohol-related traffic fatalities and to stop the "trickle down" of alcohol into Maryland's high schools.

But one of several students who objected to the measure, Steve Carlson, a 22-year-old University of Maryland senior, said, "Broad-based discriminatory laws aimed blindly at a segment of the population are not just."

The drive to raise the state's drinking age to 21--an effort thwarted for years by an intransigent House Judiciary committee and the powerful liquor lobby--seemed likely to succeed this year because of the growing number of traffic deaths related to drinking and new statistics on the increase in teen-age drunk driving.

In the House Judiciary Committee, the measure to raise the age to 21 was approved in minutes, with little of the acrimony or emotion that sunk the bill in years past.

The committee approved a compromise bill to raise the age to 21 and to "grandfather" in those persons now legally allowed to drink. Under that bill, anyone who turns 18 after July 1 would have to wait three years to drink. Anyone 18 years old before July 1 could continue to drink legally.

The so-called "phase-in" approach was recommended by Gov. Harry Hughes' task force on drunk driving and is supported by the governor.

Del. Kenneth H. Masters (D-Baltimore County), a vocal supporter of this approach, said that an immediate increase in the drinking age would spell economic ruin for some bars and taverns that now depend on 18-to-21-year-old customers. Phasing in the higher drinking age, Masters said, "gives them a chance to readjust their operations."

Before approving the phased-in 21-year-old drinking age, the panel, headed by Del. Joseph E. Owens (D-Montgomery), rejected in sequence all the alternative proposals on the issue, including a measure to raise the age to 19, and another bill to have a separate legal age for on-premises consumption and for alcohol purchased to carry out.

In the Senate, William T.S. Bricker, administrator of the state Motor Vehicle Administration and chairman of the governor's task force, said his panel backed the phase-in approach because of last year's legislative stalemate over whether the higher age should be 19 or 21.

Several senators voiced fears that raising the age in Maryland would send teen-agers to the District of Columbia, where the drinking age is 18. That fear was fueled by lobbyists from the liquor industry, who predicted that Western Maryland teen-agers would drive to West Virginia, where the legal age is 18, and Eastern Shore youngsters would drive to Delaware, where the legal age is 20.

"We're going to turn this state into a commuter state for alcohol," said Jay Schwartz, a lobbyist for the Maryland State Licensed Beverage Association.

Bricker said that raising the legal age here might prod the District into raising its legal age to 21.