The National Collegiate Athletic Association broadened substantially its opposition yesterday to a Senate bill that the organization contended would give the U.S. Olympic Committee too much power over domestic sports.

Testifying before the Senate Commerce Committee, NCAA executive director Walter Byers stopped just short of withdrawing support for the bill. At the request of Sen. Ted Stevens (R-Alaska), Byers agreed to submit proposed revisions the NCAA would find more satisfactory.

Byers also implied several times that the NCAA's decision on rejoining the USOC would hinge on the suggested changes being accepted. Other sports groups also will be offering revisions.

Byers told the hearing that the NCAA would prefer no legislation be passed and suggested that Congress, instead, observe how the voluntary USOC reorganization fares.

If Congress insists on legislation, he added, it should only codify changes the USOC already has made.

The NCAA withdrew from the USOC after the 1972 Olympics largely because the domination of the USOC by the Amateur Athletic Union, with which the NCAAA has long battled for "territorial rights" in amateur sports.

Because of the feuds between the two groups and the general disorganization in the U.S. Olympic movement, the 1977 Amateur Athletic Act was introduced in the Senate to reorganize the USOC and end, its sponsors hope, the AAU-NCAA standoff.

The latest in a series of measures with this goal, the bill is based largely upon the recommendations of the President's Commission on Olympic Sports (PCOS). The bill also would codify most of the PCOS-recommended reforms made voluntarily by the USOC last summer.

The NCAA was known to object to the Athletes' Bill of Rights. But Byers' opposition to other parts of the bill came as a surprise to the Committee, which, Sen. Richard Stone (D-Fla.) revealed yesterday, already had deleted sections objectionable to the NCAA. That was done during an informal meeting with an NCAA lawyer some time ago.

Stevens and Stone indicated those changes had been made in hopes of getting the NCAA to rejoin the USOC. Both also pointed to an NCAA news magazine that said the associations' only objection to the bill was the athletes' rights section.

Byers said the NCAA feels - and the National Federation of State High Schools took the same stance - that schools and colleges should have a veto over an athlete's competing in a non school sports contest.

The USOC has informally taken the position of allowing schools to exercise some control for academic reasons. The Senate bill would give athletes the discretion to chase the vents in which they want to participate.

Byers also said the NCAA does not object to the USOC's acting as coordinating agency for the nation's international amateur sports programs, but opposes giving the USOC any control over domestic athletics. The NCAA fears the USOC will try to regulate and schedule "restricted" events.

Although the Senate bill calls for the USOC to "direct" amateur sports in the U.S., the USOC has suggested that word be deleted to allay the NCAA's fears of a "takeover".

USOC executive director F. Don Miller said after the hearing. "The USOC has no interest in directing restricted competition." Miller was confident the issues will be resolved.

In a related matter, Sen. Howard W. Cannon (D-Nev.) said Rep. John Moss (D-Calif.), chairman of the House Oversight Committee, has agreed to conduct hearings into NCAA procedures for disciplining colleges alleged to have violated association rules.