user: Question: What is Winner, when Team is "R.J.Macarthur Onslow", and when Circuit is "Oran Park Raceway"?
Columns: ['Circuit', 'City / State', 'Date', 'Winner', 'Team']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Mallala Motor Sport Park', 'Mallala , South Australia', '7 May', 'Mark McLaughlin', 'Elfin Sports Cars']
SQL:

assistant: SELECT "Winner" FROM "Table" WHERE "Team" = 'R.J.Macarthur Onslow' AND "Circuit" = 'Oran Park Raceway';