The 21-year-old mobile front rower made eight appearances during the 2009/10 season and established himself as first choice at the Memorial Stadium for Bristol this season before suffering an injury.
"Ollie is a young English talent and is a very driven individual," said Head Coach Richard Hill. "I know he will grasp this opportunity with both hands.
"I have known Ollie for about four years now and seen him rapidly develop and come through the ranks.
"Ollie is technically excellent with his throw and a very athletic ball carrier, who likes to get around the field, and has good footwork for a front row. When he does run he also takes some stopping because he is very powerful.
"He has made himself first choice at Bristol for much of this season and we have been impressed when we have played against him this term. He is a hard worker and extremely dedicated and keen to make an impact at Warriors."
Watch new hooker Ollie Hayes in action - simply click HERE