Plan permits in service distributions at age 65. Plan also provides for annuities. Must a spouse consent to a participant's request for in service distributions?

It depends. If benefit subject to QJSA, then payment in a non-QJSA form would require spousal consent. You might want to read through IRC 417, IRC 401(a)(11)(B), and ERISA 205, as well as 1.401(a)-20, which will give you detailed information. Probably more than you want.

The Plan document should describe any necessity for spousal consent prior to distribution. Although this doesn't apply tothe OP, some DC plans which do not offer annuities still require spousal concent as per the plan document.