The American Conservative Union said yesterday that Congress moved further to the left on the political spectrum last year, matching an assessment by the group's ideological rival.

Releasing its annual ratings of congressional voting, the ACU said the House had an overall score of 37 on a 0-to-100 scale that awards high marks for votes supporting positions taken by the conservative organization. The House's overall score for 1986 was 42.

The Senate last year had 40 ACU points, a drop of 10 from 1986 before Democrats recaptured control of the chamber and brought a more liberal bend, especially from southern freshmen.

The ACU scorecard was similar to the annual congressional ratings released Wednesday by the liberal Americans for Democratic Action.

Dan Casey, ACU executive director, said that, from the ACU's standpoint, the 1987 showing by Congress was at "its lowest point during the Reagan years."

The ACU found that House Democrats had a collective score of 11, down from 20 in 1986. Republicans rose slightly, from 72 in 1986 to 74 last year.

Four Republican senators received ACU perfect marks for 1987: Phil Gramm (Tex.), Jesse Helms (N.C.), William L. Armstrong (Colo.) and Don Nickles (Okla.).

Of this group, only Armstrong received a zero in the ADA's liberal ratings. The ADA and ACU did not use all of the same roll calls in their ratings.

Eleven Democratic senators got zeroes from the ACU: Alan Cranston (Calif.), Timothy E. Wirth (Colo.), Christopher J. Dodd (Conn.), Joseph R. Biden Jr. (Del.), Daniel K. Inouye and Spark M. Matsunaga (Hawaii), Paul Simon (Ill.), Paul S. Sarbanes (Md.), Edward M. Kennedy (Mass.), Daniel Patrick Moynihan (N.Y.) and Claiborne Pell (R.I.).

In the House, 14 Republicans were rated 100 by the ACU. Zeroes went to 97 representatives, all of them Democrats except for Stewart B. McKinney (R-Conn.), who voted against ACU positions six times before his death last year.

Here are the scores of local members:

Maryland, Senate: Barbara A. Mikulski (D), 4; Sarbanes (D), 0.

Maryland, House: Democrats -- Beverly B. Byron, 35; Benjamin L. Cardin, 0; Roy Dyson, 32; Steny H. Hoyer, 0; Thomas McMillen, 4; Kweisi Mfume, 0. Republicans -- Helen Delich Bentley, 57; Constance A. Morella, 22.

Virginia, Senate: Paul S. Trible (R), 88; John W. Warner (R), 60.

Virginia, House: Democrats -- Frederick C. Boucher, 0; James R. Olin, 26; Owen B. Pickett, 22; Norman Sisisky, 39. Republicans -- Herbert H. Bateman, 74; Thomas J. Bliley Jr., 96; Stan Parris, 82; D. French Slaughter, 91; Frank R. Wolf, 87.