When was the last time all 4 of the PAC10 California schools played on the road, other than yesterday?

Answer 1

Based on what I could figure out, it was October 5, 2002.

California beat Washington 34-27 in Seattle
Stanford lost to Notre Dame 31-7 in South Bend
UCLA beat Oregon State 43-35 in Corvallis
USC lost to Washington State 30-27 in Pullman