LONDON (AP) _ A jury today convicted five Irish nationalists of plotting to blow up 16 British hotels with bombs timed to go off at the height of the 1985 summer tourist season.

Among those convicted was Patrick Magee, 35, of Belfast, Northern Ireland, who also was found guilty Tuesday of blowing up the Grand Hotel in Brighton during the Conservative Party's annual conference in October 1984.

That blast, an attempt by the Irish Republican Army to wipe out the leadership of the governing party, killed five prominent party members. Prime Minister Margaret Thatcher narrowly escaped assassination in the attack.

Today, the jury at London's Old Bailey criminal court convicted Magee, Gerard McDonnell, 34, Martina Anderson, 23, Ella O'Dwyer, 26, and Peter Sherry, 30, in connection with a foiled attempt to bomb four hotels in London and 12 hotels in coastal resorts last summer.

The five were found guilty of conspiring to cause explosions in Britain over a three-week period in July and August of 1985. Only Magee had been charged in the Brighton bombing.

All but Sherry were convicted by unanimous votes of the jury. The panel was unable to reach a unanimous verdict concerning Sherry, and the judge accepted a majority verdict for conviction of 10-2.

Judge Leslie Boreham said sentencing would be delayed for aobut two weeks pending the outcome of a related case. The details of that case were not disclosed.

During the five-week trial, the government alleged the five defendants plotted to blow up 16 hotels on consecutive days, excluding Sundays, between July 19 and Aug. 5, 1985.

Prosecutor Roy Amlot said their aim was ''to create havoc and bloodshed throughout the country.'' If successful, the bombings would have resulted in ''carnage too great to contemplate,'' he said.

Police foiled the plot after discovering plans describing the delayed- action bombs and giving the precise times and places they were to go off.

Members of Scotland Yard's Anti-terrorist Squad found one bomb hidden at the Rubens Hotel near Buckingham Palace. It was timed to go off at 1 p.m. July 29, 1985.