THE LASER SHOW has been turned off. The balloons have been deflated. Walter Cronkite is back changing sail in his boat, all the congressmen are back answering rollcalls in the Capitol.

The nation's oldest university took time out at the beginning of the month to celebrate its 350-year history. The four-day, multi-million dollar extravaganza lit up the campus, and 40,000 alumni revelers painted the town crimson.

The University--which drew attention to the big Stadium gala and the officially licensed 350th product line--took steps to try to prevent the big blow-out from looking like Statue of Liberty II. One-hundred-and-six academic symposia were scheduled and cast with an array of stars from within and without the lvory Tower. Yet, on the whole, the symposia did not place much of anything, including Harvard itself, under any serious scrutiny.

Unlike the Tercentenary Celebration in 1936, no large studies were conducted, nor were any seminal discussions convened. Both the 300th and the 350th had their share of pomp and circumstance, as they both should. But the former also saw month-long gatherings of academics making an effort to break intellectual ground.

While the address of Charles, Prince of Wales, was surprisingly engaging and Secretary of State George P. Shultz made an effort to justify the foreign policy of the Reagan Administration, only a speech by President Derek C. Bok on the role of the university in society offered any introspection. Even Bok's address was confined to generalities and did not address Harvard specifically. That address, for all its limitations, stood in stark contrast to the banality of the rest of the celebration.

The big party's over now. Another academic year--the 351st year--has begun. And it looks like it's going to be just another year. The birthday party did just what parties do: explode in an enormous burst of glitz and fade just as quickly with no real legacy. There weeks from now, undergraduates will get their own weekend of celebration, but the main event--a gala ball--is sold out. While organizers are scrambling to accommodate more students, it is likely that a substantial number will be shut out from the festivities.

What's left after the biggest party ever thrown by a university? Course catalogues with the official 350th emblem on the cover and 50-percent-off 350th t-shirt sales. What's new at Harvard? Not much.