Activists from a growing national coalition of workers and retirees rallied, marched and rang doorbells in this Corn Belt industrial city today, seeking support in their fight against the decontrol of natural gas.

But despite more than a month of planning, the young leaders of the Iowa Citizen/Labor Energy Coalition (CLEC) got indifferent results, for they were up against a foe as unassailably American as Mom's apple pie: the first home game this season of the University of Iowa football team.

The canvass here was part of a national effort to galvanize citizens in the gas decontrol controversy. The national CLEC headquarters in Chicago scheduled rallies, picketing, canvassing and marches in 60 cities in 35 states over the weekend as the culmination of a national "Gas Protest Days" effort this week. The AFL-CIO is cosponsor of the activities.

In Cedar Rapids, chief organizer Michael Lux had anticipated that several hundred residents of this quiet community of 100,000 located on a bend of the Cedar River in eastern Iowa would turn out at a march, rally and soup kitchen before canvassing in the city's residential areas.

But the morning march drew not many more than 100 and their chant of "Reagan! Reagan! He's no good, send him back to Hollywood!" fell on a downtown almost empty of passersby. Everyone seemed to be heading for the game at the Hawkeyes' stadium in nearby Iowa City or getting ready to settle down in front of a television to watch it.

An hour later, the rally-goers barely filled the first five rows of a big auditorium. And the response to the canvassers this afternoon was cordial but somewhat preoccupied: kickoff time was fast approaching.

Nevertheless, Lux, 23, said he was heartened by the turnout at the morning march and rally later in the basement auditorium of the armory, on a small islet just downstream from the Quaker Oats factory. "It's always good to have more than you expect rather than less," he said philosophically, "but these people represent a broad coalition. They are talking to each other for the first time, and that's positive."

The Iowa coalition targeted Cedar Rapids because it is in the district of Rep. Thomas J. Tauke (R-Iowa), who is on the fossil fuels subcommittee of the House Energy and Commerce Committee. The subcommittee's vote on natural gas legislation is crucial. "Turn up the heat on Tauke!" the marchers cried.

The Reagan administration contends that natural gas deregulation will lead to lower prices by encouraging exploration and increasing supplies. Opponents say deregulation will drive up prices. The national coalition wants to stop the decontrol process that began five years ago and to freeze or roll back gas prices.

A Tauke legislative aide, Ed Senn, said that the congressman does not support the decontrol of natural gas from wells drilled before 1977, but has sought a formula to allow for recovery of gas from old, played-out wells at higher prices.

On a soft, sunny afternoon in the suburb of Marion a few miles northeast of Cedar Rapids, canvasser Kymm Matthew, 23, told residents who answered her knock at the door that if decontrol is not stopped, "the gas bill for a Cedar Rapids family will go up $1,000 in three years." That was enough to get Richard Asby, a laid-off auto mechanic, to sign the Iowa CLEC petitions, which will be sent to Washington.

Asby, 23, who has a wife and two small children, said that he has been out of work for a year since being laid off by a downtown service station, which has since closed because of the continued economic downturn here. "You hardly ever hear of that happening to a gas station," said Asby.

But it is only one more sad reflection of the times here. This city, long a congenial home to major factories producing cereals, processed meat, farm implements and radios, has been hit hard by the recession. Thousands of jobs have been lost, and good times have not returned.

Asby declined to contribute to the coalition, but he and his wife wrote a letter to Tauke voicing opposition to higher gas prices that canvasser Matthew retrieved on her way home.

Most other residents among about a dozen that Matthew and Iowa state Rep. David Osterberg, a Democrat, talked with during their hour of door-to-door work either voiced support or signed the petition. But the canvass team collected only a total of $15 instead of their goal of $12 per house.

Matthew divides her time between studying law at the University of Iowa and working as a paid canvasser for Iowa CLEC. She and five other young persons spend five hours a night going door-to-door for the anti-decontrol effort. They are expected to collect $82 in donations per night, and are paid $160 a week, plus a bonus of 25 percent of anything they collect above the goal.

In its four years and eight months of existence, Iowa CLEC has grown from a shoestring operation in Des Moines to an organization with a $500,000 annual budget, 92 affiliated organizations and a membership of about 500,000.

Tamara O'Dell, the Des Moines office manager, said the coalition is about to enlarge its scope of interest to reflect its growing strength and diversity.

The nationwide deregulation protest produced proclamations and canvasses elsewhere. Michigan Gov. James Blanchard declared today and Sunday "Gas Protest Days," and said, "The natural gas situation across the nation has developed into a crisis in all areas for consumers."

Chicago Mayor Harold Washington issued a similar proclamation, saying the city "is deeply concerned about the inability of Chicago families to meet their monthly heat bills . . . ."

"People are tired to being told by politicians that there's nothing that can be done about gas bills. This is really a way they can hold accountable the people they elect," said coalition associate director Michael Podhorzer, as 50 to 75 people canvassed Alexandria, Va., to tell people their congressman, Rep. Stanford E. Parris (R-Va.), does not support the measure.

"This is a national problem, not a local problem," said William Hoyt, a Democratic state assemblyman in Buffalo, N.Y. He said natural gas prices in his economically depressed region have increased 700 percent since 1972.