Try using the FILENAME statement with the MOD option to append an existing output file.
For example, in your first code node you might have something like this:
[pre]
filename mytext "c:\temp\out.txt";
ods listing file=mytext;
proc print data=sashelp.class;
run;
ods listing close;
[/pre]
Your next code node could have this:
[pre]
filename mytext "c:\temp\out.txt" mod;
ods listing file=mytext;
proc print data=sashelp.air;
run;
ods listing close;
[/pre]
As a result, you should find that "out.txt" contains the results from both programs.
Chris