With a soft drink in hand and a confident expression on his face, Karl Schlotterbeck, head of the Montgomery Taxpayers League, recounted his latest interview, just three hours earlier, on a local TV talk show.

Schlotterbeck, who is leading a petition drive to put a tax-cutting referendum on the November ballot, had been discussing taxes with businessman Jim Goeden, president of the Bethesda-Chevy Chase Chamber of Commerce. Goeden said he opposed the leagues proposal to cut the Montgomery tax rate by a whopping 35 cents. The discussion went on for a while until, Schlotterbeck recalled. "I said to him, 'Now, Jim, it's time you said what you were for. You've been saying you're against what we do. Now, what are you for?' And lo and behold, our time was up, but his jaw just dropped."

Not everyone responds that way to Schlotterbeck and his arguments for cutting the general property tax rate in Montgomery County. But they do respond. And that is more than they did during the past brief three years of the league's history.

The Taxpayers League was formed less than three years ago in the basement of a Bethesda office building by a group of fiscally conservative county residents, all friends with a history of civic activity. There were 30 members. They would show up to testify at budget hearings held by the County Council - always with detailed mimeographed reports on how to cut the budget. They were polite and earnest.

Sometimes they stood outside the council hearing room - perhaps six of them - holding brightly colored handmade placards saying, "Cut Spending Now." Then Schlotterbeck's picture would be taken as he sat before the council testifying. The league also took pictures of their smiling members standing neatly in a row holding their paper signs. They would mail them to newspapers that would not print them.

Things are different now since California's Proposition 13 spurred angry taxpayers everywhere to protest the levels of government spending. The taxpayers league formed a committee called Tax Relief in Montgomery (TRIM). The committee started a petition drive for the required 10,000 signatures that would enable it to place a referendum on the ballot calling, for a rollback in the real property tax from $2.60 per $100 of assessed value to $2.25. The cut would be effective in fiscal 1980.

The proposal has an "escape clause" that would allow the County Council to declare an emergency need for more revenues, hold a public hearing, and then approve the increase if six out of seven council members voted for it.

The TRIM committee estimates $30-35 million would be cut from county revenues, but the county government estimates that as much as $90 million would be lost.

Now everyone wants to talk to Schlotterbeck. After the TV interview there was an interview with Washingtonian magazine. The day before, it was WRC Radio. Before that another TV interview, before that WAMU Radio. Before that other radio stations, the Kiwanis Club, etc. Last week, he spoke on a panel the league hosted at the Indian Springs Country Club before an attentive audience of 300, sitting under elegant chandeliers. Paul Gann, one of the architects of California's Proposition 13, was a panelist.

The night of the panel discussion, Schlotterbeck revealed the petition drive had already produced 15,000 signatures. That was 11 days before the petition, which must contain the signatures of 10,000 registered voters, was due to be filed on Aug. 21.

"When we started (on July 10), we had 42 calendar days," said Schlotterbeck. "We didn't know if we'd make it. We've gotten volunteers who've popped out from behind the bushes. And the calls - Rockville, White Oak, Silver Spring, Potomac, Bethesda. 'Where can we sign your petiton?' they say. We say, 'Wouldn't you like your neighbors to sign it?' And they say 'yeah." So we send them some petitions. People said they'd take them to shopping centers."

Schlotterbeck said the TRIM committee now has 200 such volunteers; the league now has a membership of 1,200. During the first two weeks of the petition drive, Schlotterbeck said he got calls at home from interested taxpayers from 6 a.m. until midnight.

Schlotterbeck estimated that, as of two weeks ago, people were being signed up at the rate of one every two minutes in some places. While Schlotterbeck was being interviewed late in the day, another completely filled petition arrived at the TRIM office. Schlotterbeck appraised it carefully. "Twelve signatures," he responded when asked how many more. "Nut that's all right. That's fine."

Schlotterbeck, a retired economist who worked for the U.S. Chamber of Commerce and, before that, for the Brookings Institute ("That was before it became a mouthpiece for the liberal wing of the Democratic Party"), said he can't remember who thought up the Montgomery referendum but that the league did it independently of Proposition 13. "This is not Proposition 13," said Schlotterbeck. "California is not Montgomery County.They're vastly different, except for one thing. They both have spendthrift governments."

Still, the success of Proposition 13 influenced the decision to push their referendum now, said Schlotterbeck and other league members.

"With the horse of the century standing at the door, we'd have been damn fools if we hadn't ridden him for all it's worth," said league member Charles Sutton, a friendly man who sports a flat-top hairstyle and string ties.

They also say their organization, admittedly low-key, has become more "active" in its approach to protesting increased revenue spending. "The County Council reacts only to organized, demonstrated anger," said Schlotterbeck. But the members still act low-key, nodding with smile about how it is true they now get more publicity than they every have before.

"I'm not publicity oriented personally," said Schlotterbeck, whose firm, low-key manner sets him apart from many other Montgomery civic activists. At 72, with his intent gaze and his deliberate, well-chosen words, ("We couldn't help but open our eyes to government; our taxbill was an eye-opener"), he seems more like a grandfatherly pediatrician than an "I'm mad-as-hell" taxpayer. He is, in fact, angry at the County Council for what he calls their "insensitivity" to the tax payer, and he constantly cites examples.

He lives with his wife off Massachusetts Avenue in Bethesda, in a one story rambler - "probably the smallest house in the neighborhood." His last tax bill was $1,500.

About the publicity he said. "It's been helpful for TRIM. If you get put in a spot of leadership, you have to be able to do what is necessary."

The constant speaking has been helpful. "I get a much better idea of how to say this," said Schlotterbeck. "It's a more succinct, less technical way to deliver this."

It has paid off. Schlotterbeck is polished, prepared, businesslike and intense. He rarely seems flustered. Only one thing seems to bother him - the fact that the league could not have more confidently gauged the response they are now beginning to receive.

"A lot of people in this county just needed some kind of a vehicle to send their messages," he explained. "If we'd had another month and not during the summer when everyone's on vacation, we could have gotten 40,000 to 50,000 signatures."

Even if the league meets its Aug. 21 deadline, then a drive to educate people and publicize the referendum must begin. Whatever happens, Schlotterbeck plans on relinquishing his position as chairman. "In another three of four months, they will get another chairman. I've been in it for two years," he said with hardly a trace of weariness in his voice. "That's enough. It's a load."