You can use m6811-elf-readelf or m6811-elf-objdump to look at the content of any object file.

To disassemble the file, you can use the following command

m6811-elf-objdump -d file.o

And if you have compiled your program with debugging information (-g or --gdwarf2) you can disassemble and show the source code with the following command:

m6811-elf-objdump -S file.o

See Also

What is readelf?