Oregon Revised Statutes Procedure in Criminal Matters Generally § 132.020

(1) Under the direction of the court, the clerk shall draw names at random from the names of jurors in attendance upon the court until the names of seven jurors are drawn and accepted by the court. The seven persons thus chosen shall constitute the grand jury.

(2) When the court, in its discretion, considers that one or more additional grand juries is needed for the administration of justice, one or more additional grand juries shall be selected in the manner provided in subsection (1) of this section.

(3) Any law applicable to the grand jury is equally applicable to any additional grand jury selected under subsection (2) of this section, except that whenever any duties or functions are imposed upon the grand jury, it shall be sufficient if such duties or functions are performed by one of the grand juries selected under this section.

(4) Any inquiry or investigation required by law to be made by a grand jury shall be void, unless such inquiry or investigation was made entirely by the same grand jury.