You can explicitly format the query to produce a delimited string with something along the lines of:
select '"'||foo||'","'||bar||'"'
from tab
And set up the output options as appropriate. As an option, the COLSEP variable on SQLPlus will let you produce delimited files without having to explicitly generate a string with the fields concatenated together. However, you will have to put quotes around strings on any columns that might contain embedded comma characters.