How early?

Usually breakfast is available from somewhere around 7 am and the bus usually leaves between 8:30 and 9:30 or so. Sometimes a little earlier, almost never later, in my experience.

And if you are doing a tour in the town, rather than getting on the bus, you will be 'on the move' by 830

Which tour are you thinking?

I found on the Best of Paris tour things got started later (like the 9:30 end of Tamara’s time frame) while tours that have a long bus day might go off earlier.

The earliest I’ve ever left was on a free day in Switzerland where the guide offered some options, one of which was to go up to the top of the Schilthorn with him. He wanted us to catch the 7:30 gondola (might have been a bit cheaper) so we left the hotel about 7:15.

Often the hotel breakfast rooms aren’t ready to start service until 7 or in some hotels, 7:30. You’d have at least 45 minutes for breakfast before departure.

Your post also made me smile. I’m currently in Yellowstone and went out early to see one of my favorite geysers. I left at 6, then when I was on my way back to my lodging after the eruption I saw a tour bus was already at one of the geyser basins at a bit after 7. The closest place they could have spent the night is at least 45 minutes away (cheap Asian tour so they don’t usually stay in park lodging), so I’m guessing a departure time of 6A for them. I can guarantee there was nothing open for breakfast in that gateway city at 5-something!

My point, and yes I have one, is that Rick won’t do that to us! If your tour needs to get moving early there is breakfast first and there’s a good reason for being on the road.

Lynn and Rock
If you go on a Rick Steves tour you will be spending a fair amount of money. You don't want to spend your valuable vacation time sleeping until 9 or 10 a.m. Most of the tours leave out between 8:00 or 9:00. If you eat the included breakfast you will need to budget at least 30 minutes to an hour before departure (and the breakfasts are usually pretty good). Is there a particular tour that you're interested in? Forum members can give you more specific tour information.