Baseball teams conspired against signing free agents after the 1986 season, an arbitrator ruled Wednesday, finding club owners guilty of collusion for a second consecutive year.

George Nicolau ruled clubs violated a provision in the collective bargaining agreement that prevents teams from acting in concert. Another arbitrator, Thomas Roberts, ruled last Sept. 21 that owners conspired against free agents between the 1985 and 1986 seasons.The Collusion II case, begun 19 months ago, centers on eight players who went past the Jan. 8 deadline to re-sign with their former clubs - Doyle Alexander, Bob Boone, Andre Dawson, Rich Gedman, Ron Guidry, Bob Horner, Lance Parrish, Tim Raines. Jack Morris, who returned to the Detroit Tigers before the deadline, is another major player in the case.

Damage hearings will be scheduled and the union is expected to ask that the players be made free agents again. The only player who waived his right to renewed free agency was Andre Dawson, who last spring agreed to a contract with the Chicago Cubs through the 1989 season.

Seven players were granted renewed free agency last winter because of the Collusion I case and Kirk Gibson left the Detroit Tigers for the Los Angeles Dodgers.

Nicolau also will decide the Collusion III case, covering free agents last winter. Testimony began July 11 and the hearing is not expected to finish before 1989.

The Major League Baseball Players Association filed the second collusion grievance on Feb. 20, 1987, charging teams engaged in systematic bid-rigging. After the grievance was filed, Dawson left the Montreal Expos for the Chicago Cubs at a $547,000 paycut and Parrish left the Detroit Tigers for the Philadelphia Phillies at a $50,000 paycut. They were the first major free agents to switch teams since Bruce Sutter left the St. Louis Cardinals for the Atlanta Braves after the 1984 season. The union alleged the free-agent market slowed because clubs agreed not to pursue free agents if the player's former club wanted him back.

Of the 79 free agents, 37 re-signed with their former clubs, 21 switched teams and 21, including Horner, did not return to the major leagues. The union alleged that except for Dawson and Parrish, the free agents who changed clubs were not wanted by their former teams.

"They didn't go after any player if the former club was still interested, no matter who the player was," union executive director Don Fehr said in March 1987.

Commissioner Peter Ueberroth repeatedly has denied the charges, saying in July: "The owners couldn't collude on where to eat breakfast."

The hearing took 39 days and heard 49 witnesses, producing 8,346 pages of transcript. In addition, 330 exhibits were presented by the union and the owners' Player Relations Committee, which defended the charges.

Dick Moss, the agent for Dawson and Morris, was the first witness, testifying on June 23, 1987. He was followed by Bucky Woy, Gary Wichard and Jack Sands, the agents for Horner, Steve Balboni and Gedman.

Economic experts hired by the union will introduce studies in the damage hearings that allege players lost $50 million to $60 million in salaries because of collusion between the 1986 and 1987 season. Part of the studies have been introduced in the Collusion I case, which is in the remedy hearing stage.