Could I have some feedback as to what other companies do to perform OQ's on there HPLC instruments? Is it better to do one's own OQ or to have a manufacture service rep come in and perform the OQ, or some combination of the two?
Thanks for your help.

What is an OQ?

If the vendor performs the OQ you could argue that they had an interest in the equipment passing the test and are therefore a biased tester! If they are to do the testing it is imperative that the testing and acceptance criteria are agreed before any work is carried out and signed by company personnel. Hope this helps.

Margaret, you wrote "If the vendor performs the OQ you could argue that they had an interest in the equipment passing".
I completely agree. Instrument users should have the same interest so that they can start as early as possible with further important validation works (e.g. System Suitability Tests, Method Transfer, Method Validation).
Nowadays it can not be acceptable to perform OQ procedures, which block the instruments for several days.
Back again to Lisas request: As long as for example your manpower is cheaper than the vendors service staff, it makes sense to perform your own OQ. Your instrument supplier is probably willing to provide you neccessary information or even training. Beside this you can find some ASTM guidelines for certain tests and books and articles about equpment qualification.
Concerning the question "What is an OQ". The OQ aberation is often used for Operational Qualification, which includes procedures and acceptance criteria for checking instruments performance. Plenty of organisations, agencies and societies have their own definition of OOQ, but in most points the definitions are equal.

An OQ is an operational qualification. It answers the question, 'is the unit operating?'. It has nothing to do with the instruments performance, which is covered by the PQ, performance qualification. e.g., to OQ an HPLC pump, one might collect the solvent at 1 mL/min for 5 min. If the collected solvent is within, say 10% of expected (4.5 mL-5.5 mL collected), then the answer to the question 'is it operating' would be yes. If it is a binary system, you would perform this test for each pump to determine that both pumps are operating. If it a single pump with low pressure gradient formation, you might collect solvent on each line to determine that the solenoid valve is operating. Questions of flow accuracy and flow repeatability are performance issues and are covered by the PQ.