AS OUTRAGES GO, the Senate Select Committee on Ethics has committed at most only a minor one by delaying any decisions on the S&L case. Perhaps it will turn out to have been no outrage at all.

The committee is looking into the role of the five senators who intervened several years ago with federal regulators in behalf of Charles H. Keating Jr. and his Lincoln Savings and Loan Association, which has since collapsed at enormous cost to the taxpayers. But the five intervened with very different degrees of force and persistence. Last month the Ethics Committee's special counsel recommended no further action against two of the five, John McCain (R-Ariz.) and John Glenn (D-Ohio). Since then, both have been pressing the committee to drop them from the investigation before the elections. Instead, the committee has decided to hold full hearings, including all five senators, after the elections.

Republicans angrily charge that the Democrats on the Ethics Committee are playing for partisan advantage. Sen. McCain is the single Republican among the five, and to exclude him would leave only Democrats in a case that has become the great national example of congressional complicity in the S&L scandals.

It's impossible to arrive at a firm judgment without knowing exactly what's in the mountain of evidence that the committee has accumulated, or what it intends to bring out in the hearings. But two things are worth noting. First, none of the five is running for reelection this year. The charge of partisanship assumes that Sen. McCain's involvement somehow rubs off on other Republicans -- and that's not very plausible. It's also true that the Ethics Committee's six members are evenly divided between the two parties, and it can't act on a purely partisan division.

The Ethics Committee has a responsibility to lay out fully and accurately this important part of the explanation of the S&L disaster. It is doing what the Senate Banking Committee might better have done, were its chairman, Donald Riegle (D-Mich.), not also one of the Keating five -- along with Alan Cranston (D-Calif.) and Dennis DeConcini (D-Ariz.), the two who, according to information so far available, were by far the most active and sedulous in responding to Mr. Keating.

This tremendous series of S&L failures happened because the S&L industry succeeded in capturing the agency that was supposed to regulate and police it. The pattern of congressional participation is increasingly clear. When is someone going to get around to the other half of the story, the part played by the Reagan administration?