If the Senate Finance Committee has voted Thursday on an administration plan to control hospital costs, the bill would probably have been defeated by an 11-to-9 vote, according to several observers. In yesterday's editions The Washington Post erroneously put the count at 11 to 2.

President Carter's program to hold down the nation's hospital costs suffered its second major blow in two days yesterday, as Chairman Russell B. Long (D-La.) postponed a Senate Finance Committee vote on it for fear that it would not pass.

Administration officials have repeatedly called hospital cost control an essential part of the Carter effort, or any effort, to expand health insurance for the poor, aged and expensively ill. And much of the opposition to the Carter hospital cost control plan comes from opponents of any extensive new health insurance system.

Long's move came on the heels of a 306-to-101 House vote Wednesday night to deny the Department of Health, Education and Welfare money to start a new system of uniform financial reporting by hospitals. While this system does not control costs, it is regarded as essential to any program that does.

Congress ordered this system started, on the urging of former congressmen John E. Moss (D-Calif.), a longtime crusader against health fraud and waste, and Paul G. Rogers (D-Fla.), long the House health subcommittee chairman.

The vote against the hospital reporting system came on an amendment by Rep. Douglas K. Bereuter (R-Neb.) to the fiscal 1980 Medicare-Medicaid appropriation. Retiring HEW Under Secretary Hale Champion yesterday called the House action a mistake, and said HEW would fight it in the Senate.

Champion called it ironic that the House would try to cripple an effort that could combat waste and help control costs on the same evening it vote 263 to 152 to require HEW to cut $500 million in alleged waste, fraud and abuse out of Medicaid and welfare funds.

HEW said last week it would have to cut Medicaid and welfare payments in the next quarter by $831 million to satisfy a similar $1 billion anti-waste amendment passed last year.

Hospital groups have lobbied hard against HEW's proposed system for hospital uniform reporting (SHUR), claiming that it would cost hospitals as much a $400 million to start it.

Dr. Clifton Gaus of HEW's Health Care Financing Administration said yesterday the start-up costs to hospitals would be no more than $65 million. He said SHUR is needed to compare hospitals' costs for X-rays, laboratory tests and so forth, "something we can't do now" for lack of information.

On hospital cost control, the Senate Finance Committee had been slated to vote yesterday on a bill by Sen. Gaylord Nelson (D-Wis.) to limit most hospitals' 1979 spending to no more than 10.9 percent above last year's.

The president had sought to limit the increase to 9.7 percent. Nelson would establish an annual rate of increase 1.8 percent higher than the extra costs hospitals can't help because of inflation.

Both the president's plan and Nelson's would set the mandatory federal limit only if hospitals fail to meet the goals of their current "voluntary effort" to limit spending.

Long had dismayed hospital and medical lobbies this month saying he would support the president's hospital cost plan.

But a Finance Committee vote, if taken yesterday, would probably have been 11 to 2 against Nelson's bill, observers said.

Among Democrats joining committee Republicans either to vote no or abstain, it was felt, would have been Long's close friend and health subcommittee chairman, Herman E. Talmadge (D-Ga.). Talmadge has his own milder Medicare-Medicaid reimbursement revision bill.

The Finance Committe has tentatively approved the Talmadge bill, but has delayed a vote on it pending action on the Nelson amendment, which could have become part of it.

The administration's hospital cost plan, though in pain in both houses, is far from dead. Nelson, blocked in committee, last year proposed a similar plan on the Senate floor, and it surprisingly passed by 47 to 42, though the House took no action.