Marshfield advanced to the OSAA 4A Football Semi-Finals with a 24-21 win over visiting La Grande Friday night in Coos Bay.  The Pirates (10-0) had to come-from-behind as the Tigers jumped out to a 13-0 lead in the first quarter.  The semi-finals have the Pirates playing Ontario, Saturday, 2:15 p.m. at Hillsboro Stadium.   Mazama and Cottage Grove will meet in the other 4A semi-final, Saturday, 4 p.m., at Grants Pass.