If I use offshore contractors, can I claim SRED Research Tax Credits?

The use of offshore contractors doesn't preclude a company from claiming SR&ED on other expenditures. However the SR&ED performed by these offshore companies would not qualify for the SR&ED tax credits in Canada.

One item of note is that a company may send employees to a foreign country to perform SR&ED activities that are related to the SR&ED work being performed in Canada. Expenditures of this nature can qualify for SR&ED but are limited to 10% of the total salaries and wages of the SR&ED claimant.