There is no specific definition for "physical" or "legal" custody in Oregon. If the parents share custody, it automatically means that they have joint legal custody and have equal rights to make all the critical decisions regarding the child. It doesn't matter whether the child lives with each parent for some specified period of time or exclusively with only one of them.
Oregon courts welcome joint custody, but it may only be awarded if both spouses want it. If there is any dispute, the court will decide custody at its own discretion, weighing such factors as the child's relationship with both parents and other family members, the interest of the parents and their involvement in the child's life before the divorce, the ability of each parent to facilitate and encourage the close relationship between the child and the other parent, any history of abuse in the family, and other facts the court may consider significant.