Democrat Michael Dukakis was heckled Saturday by gay political activists over his stand on their rights to be foster parents, while Republican George Bush fended off a corporate executive's criticism of Reagan administration policies on taxes and trade.

Both parties' presidential front-runners were spending the weekend campaigning in the West, where the the bulk of the final round of primaries will be held in the next two weeks.Dukakis, speaking to several dozen homosexual activists at a political action committee meeting in Los Angeles, promised, "You're going to be deeply involved in what we do."

But the Massachusetts governor was challenged over a policy in his state giving low priority to homosexual couples who want to be foster parents.

Dukakis said he favored the Massachusetts policy "because I think it's best, all things being equal, for a child to grow up in a household with a mother and father and other children."

His defense of that policy was met with some hisses from the crowd and occasional shouts of protest. One man shouted, "bigot," and another yelled, "You're anti-gay. Why don't you admit it?"

Dukakis later shrugged off the hostile reception, saying, "It was lively. That's what democracy is all about."

His aides, nevertheless, were pleased with the way the meeting went. "I thought it was very good, very open," said Alice Travis, national political coordinator for the campaign.

Meanwhile, Bush toured an Intel microchip plant in Oregon, where the company's board chairman, Robert Noyce, told the vice president of a need for higher taxes and for President Reagan to sign the trade bill.

"I don't think that there is any chance of a balanced budget without new taxes," said Noyce.

Reagan on Saturday repeated his vow to veto a trade bill passed by Congress because of a provision requiring large companies to notify employees in advance of plant closings.

"The plant-closing aspect of the trade bill does not seem onerous to us," Noyce said. "It is no less than we would do in any case."

Bush said he was not swayed by Noyce's arguments.