The State Senate yesterday approved a bill raising the legal drinking age in Massachusetts to 19.

The vote put the Senate bill at odds with that of the House of Representatives, which Wednesday approved a drinking age of 21 to be phased in by 1981. Unless either branch changes its position next week, the bill will go before a conference committee of the two chambers, which will try to form a compromise.

The Senate bill would make 19 the legal age for drinking in bars and for buying packaged alcohol. It would allow 18-year-olds to work as bartenders and package store clerks.

Several hundred students yesterday urged their senators to raise the drinking age only to 19. The presence of so many students "had a definite impact on rushing the bill through the Senate," Cindy L. Rubin, a Simmons College representative to the Massachusetts Independent Student Congress (MISC), said yesterday. MISC has organized many of the students.

"The legislators are trying to get the college crowd off their backs," Arthur Wing, Northeastern University's MISC representative, said this week.

Rubin added that MISC members will continue to lobby for a 19-year-old drinking age next week when the bill is in the conference committee.

Legislators opposing the 21-year-old drinking bill proposed raising the age to 19 through a parliamentary maneuver in the Senate Ways and Means committee. By an 8-1 vote, the committee discarded the House bill and sent the age 19 proposal to the Senate floor in a form difficult to amend. The Senate approved the final bill by a vote of 29-3 with two members voting "present."

Sen. David H. Locke yesterday accused Senate Ways and Means Chairman Chester G. Atkins of cheating the senators of a chance to vote for a tougher bill. Atkins later responded that the Senate voted overwhelmingly for his approach, rather than Locke's.

The vote Atkins mentioned was a 21-10 Senate decision against returning the age 19 proposal to the Ways and Means committee in favor of the House bill.

"It's a cute trick, but I think it's not a fair procedure," Locke said yesterday. But Sen. Francis D. Doris said yesterday Atkin's approach to the bill may have prevented "weeks, yes even months" of Senate debate.

Atkins said he cannot say whether Gov Edward J. King will accept the compromise Senate bill, but that the governor's staff seems amenable to the compromise.

Although students have been lobbying all week to keep the drinking age at 19, few businesses have contacted legislators about the proposed drinking age hike. Rep. Richard T. Moore said this week only one restaurant in his district has urged him to keep the drinking age at 18.