I cannot locate any information that says specifically that you are permitted to roll over installment payments made over a period of less than 10 years. But when I read between the lines of what cannot be rolled over, it seems that this qualifies as an eligible rollover distribution. Can someone verify? Thanks.

The Code defines an eligible rollover distribtion by tellying you what it is not. Section 402©(4) of the Code provides:

(4) Eligible rollover distribution

For purposes of this subsection, the term “eligible rollover distribution” means any distribution to an employee of all or any portion of the balance to the credit of the employee in a qualified trust; except that such term shall not include—

(A) any distribution which is one of a series of substantially equal periodic payments (not less frequently than annually) made—
(i) for the life (or life expectancy) of the employee or the joint lives (or joint life expectancies) of the employee and the employee’s designated beneficiary, or
(ii) for a specified period of 10 years or more,

(B) any distribution to the extent such distribution is required under section 401 (a)(9), and

© any distribution which is made upon hardship of the employee

Please note that just because the period is less than 10 years does not automatically mean that it is an eligible rollover distribution. You must also consider the life (or joint life) expectancy(ies) in making that determination.

This may be relevant to the questioner:

Gray Book 2003-27
Other DB Issues: Level Income Option and Rollovers

A plan offers a level income option. A participant elects the level income
option and receives $500 from age 55 to age 62 and nothing after age 62. Is
each payment from age 55 to age 62 eligible for rollover?

RESPONSE
Yes. Under 1.402©-2 Q3, the payments are made over a period less than 10
years and are thus eligible for rollover. If these annuity payments are not
rolled over, 20% mandatory withholding applies.