Yes, as long as you create an Amazon Alexa Enabled Group uniquely called “Everywhere” and add all your Sonos speakers by setting them as ‘preferred’ in the group, then say to Alexa … 

“Alexa, Play music (on) Everywhere” ...(just as an example)

Here is a screenshot from my Alexa App… my Alexa Group is called “Everywhere on Sonos” .. I have 10 Sonos rooms set as “preferred”… I’ve also added my non-Alexa capable devices to the 2nd middle section of the group so they will duck their audio.

I use my Alexa enabled Sonos speakers, like my Sonos Ones however, to 'enable' other Alexa Groups in my home, but they are included in the “preferred” area of this Everywhere on Sonos Group.

Thanks Ken, appreciate your reply.

Do I still need the individual groups for each speaker? Although I can’t see how I can delete these anyway.

when I add a new group titled ‘Everywhere’ the Sonos speakers are greyed out and cannot be selected. It doesn’t seem to recognise my Sonos speakers as Alexa-enabled...whereas they are voice activated Sonos Ones.

I’ve deselected them from being preferred in the other groups, but that doesn’t make any difference.

Thanks.

This is what I have set up, 1 group for each speaker (landing is below) the Kitchen panel.
 

Then when I set up an ‘Everywhere’ group the 3 speakers I want to select are greyed out. I can only select the Dot.

You are in the wrong area of the Alexa Group.. that is the 1st section for enabling the group with Alexa devices. You do not need to hit the 'edit’ button when in the Group, nor do you need to add the speakers when creating the Group.

Create the Group first without adding any speakers. Then just open the group and select, “Setup” in the “Preferred” Speaker section and you will see all your Sonos One Speaker devices to add to the group.

Just to also add that looking at your screenshot ‘Chris’s Alexa’ (an Echo Dot I assume?) appears as though it is unused as a Group Enabler/Controller, so you can possibly go onto use that to enable/control your “Everywhere” Group and by adding that to the 1st section of the Alexa group, when you make your voice request to that echo dot device you will not have to mention the Group Name … so, as an example, you just say to Chris’s Alexa ...”Alexa, Play some music” and it will automatically Group your 'preferred’ speakers and play music. 

Note you can only use an Alexa device/component once only to enable/control a group. Your Sonos devices are already assigned as controllers of your other Groups...eg. Dining Room & Kitchen.

You could of course remove your Sonos One devices from your Dining Room and Kitchen Groups and add them to your Everywhere Group and use those to Enable/Control that group instead… but this may depend on what other smarthome devices you perhaps want to control in those separate rooms/groups??? 

Thanks again Ken,

I don’t seem to be able to create a group without adding a speaker. I’ve just seen something that says a speaker can only belong to one group at a time. I tried deleting those 3 separate room groups (Do I need these?), which allowed me select the Sonos speakers in a new ‘Everywhere’ group. However, that didn’t seem to let me ask for music to be played everywhere.

I did manage to create an ‘Everywhere’ group by selecting the Dot, and then adding all 3 Sonos in the preferred speakers. Does this sound right? I don’t think I can create a group without selecting at least one of the speakers.

Thanks, sorry for my ineptness!

Sorry Ken, I’ve just spotted your latter 2 replies which probably answer my questions. I’ll have a further read and test.

thanks

Perhaps try this…

1. Create an Alexa Enabled group call it “Everywhere”  and select ‘Chris’s Alexa’ and save the Group.
2. Select/Open the “Everywhere” Group and goto “Preferred” Speaker Section and choose Setup.
3. Add all your Sonos Speakers

After a minute or so, Say to Chris’s Alexa… ‘Alexa, Play some music”

The audio should play on all your Sonos speakers.

Hope that helps

Thanks Ken,

I suppose I wanted to enable this so that in any of the 3 Sonos rooms I could ask the speaker to play individually or everywhere. (The Echo Dot is in the bedroom, and so not always within reach.)

I’ve now removed those 3 singular groups (not used for any other smart devices) and configured an ‘Everywhere’ group with the 3 speakers in, and with all 3 as preferred but still not getting the desired result.
 

Oh dear…  you’re making it rather difficult for yourself, if you want to control the speakers separately (and grouped), you will need the separate groups to also do that.

You could have just left things as they were and played the music by default to the individual (separate) Sonos rooms and then when you wanted to group them, just add the words ‘on Everywhere’ to your Alexa voice instruction.. but now you’ve deleted your individual rooms that has made it (perhaps) more difficult for yourself … I think you were better off the way I mentioned to begin with.

i would do this…

1. Remove/uncheck your Sonos One devices from the first section of the Everywhere Group, but leave them as 'preferred” in that overarching group. 
2. Put each Sonos One in its own individual Group… 'Dining Room', 'Kitchen' and 'Landing' … you can give the Groups the same names as their speaker. Not only add them to their own group, but you need to also set each one individually as the Groups 'preferred' speaker.

You can then control each room individually or …

by adding “on Everywhere” to your Alexa voice instruction, the music will play to All.

So Just to clarify you will likely need 4 groups to achieve what you’re looking for...

Everywhere .. No speaker at all enabling/controlling the group, just your 3 Sonos rooms ‘preferred’.

Dining Room .. Dining Room enabling/controlling the Group and also set as ‘preferred’.

Kitchen .. Kitchen enabling/controlling the Group and also set as 'preferred'

Landing .. Landing enabling/controlling the Group and also set as 'preferred'

What you wish do with the Echo Dot device, (Chris’s Alexa), is upto you, but I guess you could set it to perhaps enable/control one of the 4 mentioned groups. (including the Everywhere Group).