Thanks for all the replies - I can understand why people are suspecting my contractor of ignorance. That can happen, but I don't believe it to be the case this time. I think he is making sure I am happy with the outcome and have a oven that won't tip or tear out cabinet face frame. Maybe he is being over cautious.... It sounds like it is possible to just set the 27 inch oven on top of a base support instead of IN a 27 inch cabinet - is this correct? Then use some filler pieces if there is any space left exposed, right? Ok, so how would you secure the oven if you are NOT screwing clips to the face frame. If we were to anchor it to the back of the wall, it would certainly be secure, BUT, if the oven ever needed servicing or removal, would we have to remove our granite counter to get at it? Also, what should we do about supporting the granite counter above? Should we use the MDF vertical cabinet sides on either side of the oven?? I'm not at all concerned about the cost of the cabinet. It was only $130, then Home Depot gave me another $50 off when I asked about the problem with their cabinet specs. My only concerns are making sure the oven is secure with support for the granite. This oven will be adjacent to a wall, so it is at the end of a line of countertop.

I have a 36" cooktop over a 27" oven. The oven isn't actually in a cabinet proper: it sits on the plywood base built by my GC for all the cabinets, and then he created a face panel, with the appropriate size hole for the oven, and had it sprayed to match my cabinets. There's a fair bit of panel on either side of the oven, but I really don't mind: I didn't want those spice pull-outs, and wondered about making a couple of 3" tray slots, but realised the space needed internally for the hinges would make it pretty awkward to use, and I decided that offsetting the oven and getting 6" for a cabinet would look strange (in MY kitchen - that's a personal thing). So, I'm happy with my panels. I got my tray cabinet in another place in the end. I think you have to decide for yourself whether you want/need symmetry on that wall, or whether you can live without using that space for anything. In my case, it also means any subsequent owner can opt for a larger oven if they want to.

Having seen the picture, I think it will be fine. Unless the cabinets sides are exceptionally thin, cheap and weak (as in 3/8" thick) that there will be plenty strength in the cabinet even with the 1" of the 1 3/4" face frame removed. Part of the strength the face frame gives helps to prevent racking, and the adjacent cabinets will serve amply to support that cabinet. Also I'm not sure GreenDesigns concerns about self-cleaning being a problem hold up. Since the oven could be installed in a frameless 30" wide cabinet, your cabinet will have at least that much room inside the cabinet, and likely a little bit more. (Although with that said, I've never used the self-cleaning function on my 30" wall oven (which is in a 30" frameless cabinet) so I can't say it'd be OK for certain.) I do think that the shelf that will support the oven will have to be sturdy and sturdily supported. I'd use finish grade 3/4" plywood, and substantial blocking beneath the shelf to support it -- possibly even 1/2" plywood sheets that reach from front to back of the cabinet and from the floor of the cabinet to the base of the oven shelf. Plus one across the back of the cabinet, and a new face frame piece across the front of the shelf.

Yes, it will probably work. Today most brands design both their wall ovens and cooktops to be used in this configuration, so usually similar models will work together. Realistically, even different models will usually work, electric cooktops just aren't that deep and the only worry becomes electrical hookup for the cooktop. I used a 24" cooktop for years in a foreign country and didn't find it to be bothersome. In fact, I preferred it sometimes (in full disclosure, don't like it enough to actually replace our current range with one). Ours was similar to the Bosch 500 series and really it just eliminated the open space between pots, the purpose of which is apparently to be dripped on and annoying to clean while cooking. If you are comparing a 24" cooktop to a 30" with offset burner designs (which you want if you actually cook) you do lose one left hand stir on the back left burner. However, only left handed people actually use the left hand stir, so just FYI. If you are doing it, do not skimp on your cooktop, saving money and saving space don't go well together.