Another option is just using head:
grep ...parameters... yourfile | head
This won't require searching the entire file - it will stop when the first ten matching lines are found. Another advantage with this approach is that will return no more than 10 lines even if you are using grep with the -o option.
For example if the file contains the following lines:
112233
223344
123123
Then this is the difference in the output:
$ grep -o '1.' yourfile | head -n2 11 12 $ grep -m2 -o '1.' 11 12 12
Using head returns only 2 results as desired, whereas -m2 returns 3.