From Page 3 of Bob's 1999 Q&A here:
I was reading one of the (unfortunately few) articles on the Penguin, and one of them made reference to Lindsey and Stevie's joining the band while you were still a part of it. Had you already left the band by the time L&S joined? I know you eventually worked with them, but when did you actually meet Lindsey and Stevie? (Tracy G., Stockbridge, Georgia, USA)
I "hemmed and hawed for months about whether or not I would leave FM... John Mc Vie said, " Bob it'll be the biggest mistake you'll ever make." Everybody knew that we had to find some new creative "juice". Mick had gone out to check out studios to do the next album after "Heroes..." while I was still hemming and hawing. At "Sound City" studios is where somebody played him a tape of Stevie and Lindsey as "Bucking-Ham Nicks". Mick told me about hearing their tape, and how good they were etc. At that point I could've chosen to stay in FM, and add Stevie and Lindsey to the line up. It wasn't like anybody was ASKING me to leave, and there was a moment that I thought about staying.
In case it helps?
John