sponsor 401(k) and SEP at same time?

Can an employer sponsor a 401(k) and a SEP at the same time?

Only 3 employees plus owner (who gets no compensation except health insurance reported on K-1 as guaranteed payments).

One employee long-term, other two employees less than 3 years service.

Owner wants to reward long-term employee but doesn't want to create big taxable income for him, so considering doing a SEP contribution.  Long-term employee would meet 3-of-5 years eligibility but other two employees would not for the current year.

Thanks.

You can have a SEP and a qualified plan but cannot use the IRS model SEP (or whatever the proper description) and must use a provider SEP document, the terms of which allow for sponsorship of another plan.