The 6-foot-10 Moreland averaged 9.4 points and a team-leading 10.6 rebounds a game last season. Collier averaged 12.6 points and six rebounds. Both players will also miss the team's exhibition games.
Robinson announced in July that the players had been suspended indefinitely for undisclosed violations of team rules. He did not disclose the length of the punishment until Tuesday.
Moreland's lengthy suspension is a huge blow for Robinson, who enters his sixth season in Corvallis and is coming off a 14-18 campaign in which the Beavers were 4-14 in the Pac-12.
Oregon State also lost starting guard Ahmad Starks, who transferred to Illinois for his final season. The Beavers will have Angus Brandt, a 6-10 senior from Australia who averaged 11.3 points and 8.5 rebounds through four games last season before suffering a torn ACL.