Can guinea pigs eat oats?

[Cookie Trio]

So my dad asked me the other day if guinea pigs can eat oats, so I searched it up and the answer was no (because it is a grain). Then yesterday I was looking through some treat recipes here on the forum and many of them included oats. The recipe looked really good and I want to try it but i'm not until I find out if oats are suitable.
Thanks to anyone that can help!
I live in Bedfordshire
I have three male guinea pigs

 

[Piggies&buns]

Yes they can eat them but I wouldn’t give them as routine. Oats are high calorie and can be useful for helping piggies who have been poorly in regaining some lost weight.

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[Cookie Trio]

Thank You